Hatano Y., Katsumura Y., Mozumder A. (Eds.) Charged Particle and Photon Interactions with Matter - Recent Advances, Applications, and Interfaces

Подождите немного. Документ загружается.

790 Charged Particle and Photon Interactions with Matter

where

is the excitation cross section

is the photoelectron ux, both evaluated at energy, E

The

cross section can be written as the product of the peak cross section and ϕ, the normalized

energy

function: σ = σ

peak

ϕ(E). Then

g z E F z E dE z

ex ex

peak

( ) ( ) ( , ) ( )= =

∫

σ φ σ γ

(28.15)

where γ(z) describes the altitude dependence of the g-factor. If γ is the same for excitation and emis-

sion (i.e., the energy functions are the same or the energy dependence of F does not change with

altitude),

then the a-state volume emission rate can be dened in a similar manner:

j z n z g z n z E F z E dE n z

em N em N

N eff

eff

( ) ( ) ( ) ( ) ( ) ( , ) ( )≡ = =

∫

2 2 2

σ φ σ γ(( )z (28.16)

where

eff

is dened as the effective peak cross section for emission from the a state, including

cascade

components.

Substitution

of Equations 28.13 through 28.16 into Equation 28.12 gives the following relation-

ship

for the effective emission cross section:

σ γ σ γ

eff

N ex

( ) ( ) ( ) ( )

( )

z n z B z n z

j z

2 2

1= + +

′

( )z













(28.17)

σ σ

eff

= + +













j z

′

( )

(28.18)

Next the Atmospheric Ultraviolet Radiance Integrated Code (AURIC; Strickland et al., 1999) model

was used to calculate thermospheric volume excitation rates (without cascade) using the latest Young

et al. (2010) and Johnson et al. (2005b) cross sections for a, a′ and w states at several solar activity

and illumination conditions (Evans, 2010). We found that the ratios for a′/a and w/a (using shorthand

notation for the ratios of volume excitation rates) are nearly independent of altitude between 150 and

250km (to within ± 5%) where the bulk of the dayglow originates, and equal 0.134 and 0.172, respec-

tively. Substituting these into Equation 18, the effective a-state emission cross section becomes

eff

= 0.8771 × 1.98 × 10

–17

× (1 + 0.134 + 0.174) = 1.74 × 10

–17

× [1 + 0.31], or σ

eff

= 2.28 × 10

–17

. Thus, our estimate indicates an a-state emission cross section enhancement of 31% by cascade.

Our simplied estimate can be compared with the much more detailed calculations of Cartwright

(1978) and Eastes (2000). Cartwright (1978) modeled the vibrational populations of a variety of N

states in an IBC II Aurora. His direct a-state excitation cross section was 3.02 × 10

−17

(surpris-

ingly the same as AS85). His Figure 28.18, left panel, displays the vibrational populations of the

a-state for direct excitation and cascade from the a′- and w-states, for altitudes of 110km and >130km.

Cartwright found little change in the percentage cascade contributions and fractional populations

above 130km, thereby supporting the assumption used in our derivation of the effective cross section.

Using Cartwright’s >130km case, we can estimate an effective emission cross section from his work.

Summing the population rates for each vibrational level of the three states, we nd total population

rate ratios of a′/a = 0.60 and w/a = 0.13. The total is 0.73, more than twice our value, as expected

from his larger cross sections. We obtain a similar value for the total cascade enhancement using the

Trajmar etal. (1983) renormalization of the Cartwright cross sections, although the individual contri-

butions from a′ and w are different.

UV Molecular Spectroscopy from Electron Impact for Astrophysics 791

Eastes (2000) carried out a more detailed calculation of the LBH emission rate that included

cascade. According to his Table 28.1 a peak excitation cross section of 2.69 was used. The conclusions

of his paper state that the calculated emission rate with cascade is 55% larger than with excita-

tion alone (i.e., without cascade). The effective cross section becomes 2.69 × 1.55 × 0.8771 = 3.66,

somewhat larger than ours. But using the Johnson et al. a′ and w cross sections, his cascade would

become 22% and the effective cross section becomes 2.9 × 10

–17

, closer to our derived value.

Cascade rates from a′- and w-states to the a-state shown in Figure 28.4 of Eastes (2000) vary

strongly with altitude below about 200 km. This is discrepant with Cartwright (i.e., small varia-

tions above 130km) and with the ratios of excitation rates from AURIC (although there may be

some altitude-dependent effect in the cascade rates that could cause the emission rate ratios to

differ from the excitation rate ratios). This discrepancy has not been resolved. A possible explana-

tion is that Eastes used the Continuous-Slowing-Down photoelectron model of Jasperse (1976),

whereas the AURIC photoelectron model is much more physically realistic. If the Jasperse model

produces much greater altitude variations in the photoelectron ux energy dependence, it could

account for the different behavior. Eastes also calculated the effect of collision-induced electronic

transitions, but these should not be of much signicance in the dayglow that is produced at higher

altitudes where collisions are infrequent.

Budzien etal. (1994) analyzed dayglow observations of the LBH band system. They used the

AS85 excitation cross section corrected for the revised H

standard (2.7 × 10

−17

). They found

that the total excitation rate had to be increased by a factor of 1.45, which when adjusted for predis-

sociation, yields an effective emission cross section of 1.45 × 2.7 × 10

−17

× 0.8771 = 3.5 × 10

−17

larger

than ours by 54%.

Young

et al. (2010) estimate the effect of cascade based on the ratios of cross sections: (a′ + w)/

a = 0.48 at 15 eV and 0.29 at 20 eV. Our value using volume emission rate ratios of 0.31 is quite close

their estimate. Their effective emission cross section is given in Table 28.5.

summary, we have made a simple estimate of the effective emission cross section that can be

used to adjust the a-state excitation cross section for the effects of cascade from the a′- and w-states.

Other determinations of the emission cross section based on either AS85 or Cartwright range are

mostly higher than our derivation, because the more recent cross section measurements are lower

than they used. Consequently, we recommend the use of σ

eff

= 2.28 × 10

−17

at the peak at 20eV

the effective LBH emission cross section to account for the effect of cascade into the a-state.

Clearly,

new measurements are needed to quantify the effect of cascade in the LBH system.

As well, more modeling efforts are called for. Our estimate was based on a variety of simplifying

assumptions and a single dayglow case. The work of Cartwright and Eastes needs to be repeated with

more accurate photoelectron and auroral uxes under a variety of geophysical and solar conditions.

Another potential source of error in applying LBH cross sections to conditions where the ener-

getic electron ux is changing rapidly with energy is the threshold effect. Thresholds for different

vibrational levels are spread from 9 to 15eV for the v″ = 0 → v′ manifold. With increasing electron-

impact energy, the cross section for each vibrational level rises very steeply in the low-energy region

where measurement uncertainties are generally large (Note that the Young et al. cross section data

in Figure 24.21 are for the (3.0) vibrational transition.). Accurate laboratory measurements are

needed near threshold energies using a high-resolution electron gun with electron beam energy

spread

of ΔE

≈ 100 meV.

Although this chapter focuses on molecular process, we digress briey to consider the status of

electron-impact excitation of atomic oxygen to the

state. The subsequent emission at 135.6nm

is used by aeronomers along with the LBH bands to measure the O/N

column density in the

thermosphere. Its absolute signal is a measure of the solar energy input to the atmosphere in the

Earth’s dayglow. A literature review shows that there exists only one measurement (Stone and Zipf,

1974) and one theoretical calculation (Julienne and Davis, 1976) of OI 135.6nm cross section of O

reported more than 30 years ago and they differ by a factor of two. Meier (1991) scaled the Stone and

Zipf measurement downward by a factor 0.36 to account for the improved determinations of the OI

792 Charged Particle and Photon Interactions with Matter

130.4nm emission cross section that was measured simultaneously with that for 135.6nm by Stone

and Zipf. His recommended value for the peak cross section is 9 × 10

−18

at 16eV. A validation

of the old laboratory measurement of the emission cross section of O I (135.6nm) is strongly needed

as is an evaluation of the large cascade contributions. Since electron impact is the dominant excita-

tion process in the dayglow and aurora, its cross section remains one of the outstanding missing

parameters needed for reliable aeronomical remote sensing. Given the revision of the effective LBH

emission cross section from that of AS85, the airglow algorithms need to be reconsidered.

28.4.5 co

As the most abundant interstellar molecule after H

, CO plays a very important role in the photo-

chemistry of the ISM. The abundance ratio of CO to H

is difcult to obtain from observations of

the ISM, but can be determined from theoretical models. The models involve chemical reactions in

which photodissociation by vacuum ultraviolet (VUV) radiation is the main destruction mechanism

for CO, particularly in the range between 91.1 nm, the edge of atomic H absorption continuum, and

111.8 nm, which is the dissociation limit of CO into ground state atoms. The rate of photodissocia-

tion of CO by EUV radiation is one of the major uncertainties in these models. In view of these

uncertainties and the importance of CO as a tracer molecule, a large number of experimental stud-

ies aimed at nding coincidences between CO molecular absorption lines and molecular hydrogen

emission

lines have been performed (Ciocca etal., 1997a,b).

large disparity in the values of the oscillator strengths of the A−X, B−X, C−X, and E−X exists in

the literature. To resolve the discrepancies, we have carried out high-resolution EUV measurements of

these states to determine predissociation yields and oscillator strengths (Ciocca et al, 1997a,b; Beegle

etal., 1999). In Figure 28.22, we show for states we have studied, the potential energy diagram of

Rydberg states lying above the A

Π valence state. The internuclear distance of the minima in the poten-

tial curves of the Rydberg states overlies exactly the minima of the ground state, resulting in intense

(0,0) bands. With a full-width-at-half-maximum (FWHM) of 0.0036nm, we can resolve the rotational

structure of the B(0,0), C(0,0), and E(0,0) bands. We show the rotational structure for these (0,0) diagonal

bands in Figure 28.23. We also show a model of these bands. A simple model based on Honl-London

factors (Ciocca etal., 1997a,b) and rotational constants matches the observed spectra. The predissocia-

tion yield of 88% is found for the E

Π state, an average of 85% for the Π

state, and 91% for the Π

−

state.

The CO A−X band system emission spectrum has been observed in the airglow spectrum of Mars

and Venus between 120 and 180nm (Feldman etal., 2000). Longward of 125nm, the UV spectra of

both planets are dominated by the emission of CO fourth positive band system (A → X) and strong

O I and C I multiplets. In addition, CO bands, B

−X

(0, 0) at 115.1nm and C

−X

(0, 0)

at 108.8nm, are detected, and in the spectrum of Venus, there is a weak indication of the E

Π−X

(0,0) band at 107.6nm. The production mechanism of excited CO(A) molecules in the thermo-

sphere is attributed to the photodissociation of CO

by solar EUV shortward of 92 nm. The CO A−X

band system is excited by the impact of photoelectrons and absorption of solar UV photons by both

CO and CO

(Barth etal., 1992). We have reported electron-impact-induced, medium-resolution

uorescence spectra (0.0031 and 0.00366nm FWHM) of CO at 100eV over the spectral region of

130–205nm (Beegle etal., 1999). The features in the FUV emission spectra correspond to the fourth

positive band system (A

Π−X

), atomic multiplets from C and O, and their ions. The absolute

electronic transition moment was determined as a function of internuclear distance from relative

band intensities. The excitation function of the (0,1) band (159.7 nm) was measured from electron

impact in the energy range from threshold to 750eV and placed on an absolute scale at 100 eV,

as discussed in Section 28.3. The CO A–X band system emission cross section was established

from a measurement of the relative band intensities at 100 eV. We have obtained high-resolution

(∼0.0034nm FWHM), second-order spectra of the A(0,1) band at 159.7nm from CO by direct exci-

tation and from CO

by dissociative excitation. The fourth positive bands produced by dissociative

excitation are signicantly broader and hotter (300K vs. 1400K) than direct excitation at laboratory

UV Molecular Spectroscopy from Electron Impact for Astrophysics 793

temperatures. A resolution of ∼0.2nm of CO band structure is sufcient to distinguish the two types

excitation mechanisms in a planetary atmosphere of known thermospheric temperature.

28.4.6 So

Jupiter’s Io tenuous atmosphere is dominated by molecular SO

and its dissociation products SO,

S, O, and probable emissions from sulfur allotropes, S

(S, S

,…). A detailed model of the auroral

processes at Io requires, as a rst step, a medium-resolution laboratory study of both S

and SO

as a function of energy to match the spectral dependencies of ground-based spectral observations

(Bouchez etal., 2000), as well as the Galileo SSI observations of the blue Io auroral glow on E15

(Geissler

etal., 1999). To date, S

has not been successfully studied in the UV.

Atomic and molecular data have been used most recently in the analysis of the Galileo Solid

State Imaging observations of Io (Geissler etal., 1999), Cassini spacecraft observations of Io by

the ISS (Porco etal., 2004; Geissler etal., 2004) and the UVIS (Esposito etal., 2005). The ISS is

equipped with 15 lter combinations that span the wavelength range of 235–1100nm. From the

data acquired during the Jupiter Millennium Cassini encounter, Geissler etal. (2004) performed a

detailed comparison of laboratory SO

spectra with the Cassini ISS observations and inferred that

a mixture of gases contribute to the equatorial glow. The equatorial glows were particularly bright

in the near- UV wavelengths (230–500nm) lters UV1, UV2, UV3, and Blue1. Based on the labora-

tory work of Ajello etal. (1992a,b), the relative emission intensities within each band pass conrm

12.0

11.0

10.0

1.0

0.8 1.3

B(0,0)

E(0,0)

C(0,0)

r (Å)

No predissociation

100% emission

Partial

predissociation

emission

No emission,

>99% predissociation

C (

P)+O (

1.8 2.3

1,3,5

–

1,3,5

Figure 28.22 Simplied potential energy diagram for CO RV states (Ciocca etal., 1997).

794 Charged Particle and Photon Interactions with Matter

SO (A–X)

(A, B, α–X)

98 eV

Laboratory MUV spectrum

of electron excited SO

18 eV

8 eV

–1

200 240 280 320 360 400

Wavelength (nm)

Relative intensity (arb. units)

440 480 520 560 600

Cassini ISS filters

UV1 255

300

340

445

440

562

105

145

Filter Center FWHM nm

UV2

UV3

BL1

BL2

GRN

Filter 8 eV 18 eV

Electron energy

0.34

0.42

1.00

0.39

0.20

98 eV

0.3

0.41

1.00

0.79

0.97

ISS

<1.0 (SO

)

0.30 (SO

)

1.00

0.93 (S

0.96 (O, Na?)

0.0

0.33

1.00

0.27

0.29

UV1

UV2

UV3

BL1

GRN

Intensity

Figure 28.24 The calibrated SO

electron-impact-induced uorescence spectra were obtained at 8, 18, and

98eV electron-impact energy and a spectral resolution of 1.8nm over the wavelength range 200–600nm. The

two tables present the Cassini ISS lter band passes and the fraction of electron-impact-induced uorescence

of SO

emission signal expected in each lter band pass normalized to unity at lter UV3 (Geissler etal., 2004;

Ajello etal., 2002b).

1.25

1.00

0.75

0.50

Relative intensity (arb. units)

0.25

1149.2 1149.6 1150.0 1150.4 1150.8

Wavelength (Å)

CO(X

)+ e (30 eV)

CO(X

)+ e (75 eV)

CO(E

Π)+ e

hν

0,0

hν

0,0

Δλ

FWHM

=36 mÅ

Δλ

FWHM

=36 mÅ

CO(B

)+ e

Wavelength (Å)

1151.2 1151.6 1152.0 1074.0 1074.8 1075.6 1076.4 1077.2 1078.0

1.00

0.75

0.50

0.25

Data

Model

Data

Model

Relative intensity (arb. units)

hν

0,0

Wavelength (Å)

1086.5 1087.0 1087.5 1088.0 1088.5 1089.0 1089.5

1.00

0.75

0.50

0.25

CO(X

)+ e (100 eV)

Data

Model

CO(C

)+ e

Δλ

FWHM

=36 mÅ

Figure 28.23 High-resolution EUV spectra of CO (B,C,E → X) (0,0) bands: data(solid) and model (dash).

The

FWHM is 36

mÅ

(Ciocca etal., 1997).

UV Molecular Spectroscopy from Electron Impact for Astrophysics 795

the presence of molecular SO

in the Io atmosphere. The laboratory SO

electron-impact-induced

uorescence spectrum is shown in Figure 28.24 along with a table that lists the UV, middle UV, and

visible lters, and a comparison of the laboratory relative intensities at 8, 18, and 98eV normalized

to UV3 intensities. There is an agreement between the measured output of 100 kR from lter UV3

and the 8 and 18eV relative intensities within the same band-pass, e.g., the laboratory peak intensity

at 320 nm agrees closely with the UV3 lter centered at nearly the same wavelength. There is a

Blue1

discrepancy and Green elevated due to the possible atomic emissions indicated in the table.

The

laboratory work of Ajello etal. (2002b) used in the Cassini ISS comparison only covered the

wavelength range of 200–600nm. Most of the ISS lters from the blue to the near-IR (500–1200nm)

range show substantial emission intensities as well. We have recently expanded our wavelength cov-

erage to include the entire range of 200–1100nm using newly acquired laboratory spectroscopic

instrumentation that closely matches the Cassini ISS wavelength capability (Ajello etal., 2008).

This added coverage is the rst study of SO

from the UV, visible, optical to near-IR range, i.e., the

entire

VOIR, which is needed to conrm the model analysis of Geissler etal. (2004).

The

Cassini spacecraft at Io and Jupiter during the Cassini Campaign has repeated a spectac-

ular series of visible/near-IR auroral observations similar to those obtained by Galileo SSI but

at improved spectral resolution. We show in Figure 28.25 the initial multi-spectral image of Io

To Jupiter

Pele

Pillan

Tvashtar plume

(a) (b)

Figure 28.25 Multispectral Image of Io during eclipse of January 1, 2001. (a) False color composite made

up of IR4, CB1, and UV3 lter-images portrayed in color in the original work of Geissler et al. 2004 as red,

green and blue, respectively. We portray the multi-spectral image in a grey scale with the small circular

volcanic feature in right-center from Pele as ‘red’ IR4, outer ansa and circular limb glow is mostly ‘green’

UV3, inner ansa glow is ‘blue’ CB1. (b) CB1 (red) and UV3 (blue) images superposed on clear lter image.

locations

of volcanoes and plume glows discussed (Geissler et al., 2004).

796 Charged Particle and Photon Interactions with Matter

obtained during the eclipse of January 1, 2002 showing a false color composite of the equatorial and

limb

emissions (Geissler etal., 2004).

Besides

being a scientic destination in its own right (Galileo and JUNO), Jupiter is used for

gravitational assist trajectories to the outer solar system (e.g., the Cassini and New Horizons mis-

sions). Consequently, UV observations of the Jovian system are also taking place periodically as

secondary mission objectives. Active magnetospheres are coupled to the ionospheres of the giant

planets’ systems and produce particle-excited aurora and airglow. Trapped particle impact on a

planetary satellite atmosphere can result in global excitation, both day and night. For Io, having

a volcanically generated SO

atmosphere, dissociative excitation by the magnetospheric Jovian

plasma torus results in excited SO, S, and O, in addition to excited SO

and ions, all of which emit

radiation. It is believed that the bulk of Io’s atomic emission is powered by electron excitation of

neutral S and O directly, rather than by the electron dissociative excitation of SO

(Ballester etal.,

1996). A visible image of Io is shown in Figure 28.26 along with an HST/GHRS spectrum in the

FUV with spectral identications (Ajello etal., 1992a,b; Clarke etal., 1994). There is an evidence,

however, that both direct excitation of S and O and dissociative processes upon SO

contribute to

the Io emission spectrum: (1) Oliversen etal. (2001) indicate that short-term uctuations in the O I

630nm intensity is the evidence for a high-energy, nonthermal plasma tail (∼30eV) for a one-step

process, and (2) Ballester (1998) indicates that neither electron excitation of O I nor electron dis-

sociative

excitation of SO

alone by plasma electrons can explain the HST or IUE observations.

28.5 ConClusions

UV emission spectroscopy by electron-impact-induced uorescence has been reviewed for a few

molecules of major importance to astronomy and planetary atmospheres. The laboratory goals

are to (1) measure electron-impact emission cross sections (0–2keV) and uorescence spectra

(50–300nm) for important atoms and molecules key to remote sensing observations of FUSE

0.3

0.2

1200 1300 1400

Wavelength (Å)

1500

1200 1300 1400

Wavelength (Å)

1500

S,O O S S

~1–2 kR

S S,O O S S

~300 R

Io in sunlight

Io in shadow

FOS G13OH counts/sFOS G13OH counts/s

0.1

0.0

0.06

0.04

0.02

0.00

Figure 28.26 Voyager visible image of Io by HST showing an active volcano and HST GHRS FUV spec-

trum

of Io with tick marks at strong atomic emission lines of sulfur and oxygen (Clarke etal., 1998).

UV Molecular Spectroscopy from Electron Impact for Astrophysics 797

(Far Ultraviolet Explorer), HST (Hubble Space Telescope), HUT (Hopkins Ultraviolet Telescope),

TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics), Galileo, Cassini, and

many other spacecrafts; (2) emphasize recently observed and relevant UV transitions of cosmically

abundant species of Jovian and terrestrial planetary systems, ISM, and comets (e.g., H, H

, HD, N

, O, CO, and O

); (3) provide collision strengths in analytical form or tables of cross sections

for UV radiative processes for electron energy loss transport codes and for comparison to ab initio

calculations; and (4) study corresponding VOIR cascade transitions (300–1100nm or 1–5eV excita-

tion

energy).

summary of salient planetary observation results from recent studies of the important atoms

and molecules employing the ESL database are listed below:

• The rst analysis of the Cassini UVIS observations of the Saturn H

aurora (Esposito etal.,

2005) and the rst analysis of the Jupiter millennium H

aurora observations (Ajello etal.,

2005a).

• The rst analysis of the Cassini Io visible aurora observations of predominantly SO

by the

ISS

(Geissler etal., 2004).

•

The development of atomic and molecular hydrogen models used in the interpretation

of low-resolution Galileo spectra, medium-resolution HUT spectra, and high-resolution

FUSE and HST UV spectra of Jupiter (Dols etal., 2000; Ajello etal., 2002a, 2005a; Gustin

etal., 2002, 2004).

• The analysis of Galileo Solid State Imaging (SSI) H

VOIR observations of Jupiter

(Vasavada

etal., 1999).

•

The modeling of Cassini and STIS/GHRS (Goddard High Resolution Spectrometer) UV

observations of Io, Europa, and Ganymede (Trafton etal., 2007; Noren etal., 2001a,b;

Vatti

Palle etal., 2004; Hansen etal., 2005).

•

Resolved longstanding V1 UVS ambiguity on Titan EUV spectral content showing that

the N

Carroll-Yoshino

′

(0,0) band (Broadfoot etal., 1981b) was undetectable and NI

photodissociative ionization (PDI) multiplets were present instead (Ajello et al., 2007;

Stevens

etal., 1994).

aCknowledgments

The research described in this chapter was carried out at the Jet Propulsion Laboratory, California

Institute of Technology, and was sponsored by the NASA Planetary Atmospheres, Astronomy and

Physics Research and Analysis, Cassini Data Analysis and Heliophysics Research Geospace Science

Program

Ofces, and NSF Aeronomy Program Ofce Under Grant Number 0850396.

reFerenCes

Abgrall, H., Roueff, E., Launay, F., Roncin, J. Y., and Subtil, J. L. 1993a. Table of the Lyman Band system of

molecular

hydrogen. Astron. Astrophys. Suppl. 101: 273–321.

Abgrall,

H., Roueff, E., Launay, F., Roncin, J. Y., and Subtil, J. L. 1993b. Table of the Werner Band system of

molecular

hydrogen. Astron. Astrophys. Suppl. 101: 323–362.

Abgrall,

H., Roueff, E., Launay, F., Roncin, J.Y., and Subtil, J. L. 1993c. The Lyman and Werner Band systems

molecular hydrogen. J. Mol. Spectrosc. 157: 512–523.

Abgrall,

H., Roueff, E., Launay, F., and Roncin, J. Y. 1994. The B′

→ X

and D

→ X

band sys-

tems

of molecular hydrogen, Can. J. Phys. 72: 856–8.

Abgrall,

H., Roueff, E., Liu, X., and Shemansky, D. E. 1997. The emission continuum of electron-excited H

Astrophys. J.

481: 557–566.

Abgrall,

H., Roueff, E., Liu, X., Shemansky, D., and James, G. 1999. High-resolution far ultraviolet emission

spectra

of electron-excited molecular deuterium. J. Phys. B: At. Mol. Opt. Phys. 32: 3813–3838.

Abgrall,

H., Roueff, E., and Drira, I. 2000. Total transition probability of B, C, B′ and D states of molecular

hydrogen.

Astron. Astrophys. Suppl. Ser. 141: 297–300.

798 Charged Particle and Photon Interactions with Matter

Aguilar, A., Ajello, J. M., Mangina, R. S., James, G. K., Abgrall, H., and Roueff, E. 2008. The electron excited

middle UV to near-IR spectrum of H

: Cross sections and transition probabilities. Astrophys. J. Supp.

Ser.

177: 388–407.

Ajello,

J. M. 1970. Emission cross sections of N

in the vacuum ultraviolet by electron impact Source. J. Chem.

Phys.

53: 1156–1165.

Ajello,

J. M. 2010. High resolution spectra of N

. (in preparation).

Ajello, J. M. and Shemansky, D. E. 1985. A re-examination of important N

cross sections by electron impact

with application to the dayglow: The Lyman-Birge Hopeld band system and NI (119.99 nm).

J.Geophys. Res.

90: 9845–9861.

Ajello,

J. M. and Shemansky, D. E. 1993. Electron excitation of the H

−

) continuum in the vacuum

ultraviolet.

Astrophys. J. 407: 820–825.

Ajello,

J. M. and Ciocca, M. 1996a. Fast nitrogen atoms from dissociative excitation of N

by electron impact.

J. Geophys. Res.

101: 18953–18960.

Ajello,

J. M., Shemansky, D., Kwok,

L., and

Yung, Y.

L. 1984. Studies of extreme ultraviolet emission from

Rydberg

series of H

by electron impact. Phys. Rev. 29: 636–653.

Ajello, J. M., Pang, K. D., Franklin, B. O., Howell, S. K., and Bowring, N. J. 1989a. A study of electron impact

excitation

of NO:

The

vacuum ultraviolet from 40 to 170

nm.

J. Geophys. Res. 94: 9093–9103.

Ajello,

J. M., James, G. K., Franklin, B. O., and Shemansky, D. E. 1989b. Medium resolution studies of EUV

emission from N

by electron impact: Vibrational perturbations and cross sections of the c

′

and b′

states. Phys. Rev. A. 40: 3524–3556.

Ajello, J. M., James, G. K., Franklin, B., and Howell, S. 1990. Study of electron impact excitation of Argon

in the EUV: Emission cross sections of resonance lines of Ar I, Ar II. J. Phys. B: At. Mol. Opt. Phys. 23:

4355–4376.

Ajello, J. M., James, G. K., Kanik, I., and Franklin, B. O. 1992a. The complete UV spectrum of SO

by electron

impact:

Part 1:

The

vacuum ultraviolet spectrum. J. Geophys. Res. 97: 10473–10500.

Ajello,

J. M., James, G. K., and Kanik, I. 1992b. The complete UV spectrum of SO

by electron impact: Part 2:

The

middle ultraviolet spectrum. J. Geophys. Res. 97: 10501–10512.

Ajello,

J. M., Ahmed, S., Kanik, I., and Multari, R. 1995a. Kinetic energy distribution of H(2p) atoms from

dissociative

excitation of H

. Phys. Rev. Lett. 75: 3261–3264.

Ajello, J. M., Kanik, I., Ahmed, S. M., and Clarke, J. T. 1995b. The line prole of H Lyman-α from dissociative

excitation

of H

with application to Jupiter. J. Geophys. Res. 100: 26411–26420.

Ajello, J. M., Ahmed, S. M., and Liu, X. 1996b. Line prole of H-Ly-β from dissociative excitation H

. Phys.

Rev.

53: 2303–2308.

Ajello,

J. M., James, G. K., and Ciocca, M. 1998a. High resolution EUV spectroscopy of N

c′

ν′ = 3 and

levels by electron impact. J. Phys. B. 31: 2437–2448.

Ajello,

J. M., Shemansky, D., Pryor, W., Tobiska, K., Hord, C., Stephens, S., Stewart, A. I., Clarke, J.,

Simmons,K., Gebben, J., Miller, D., McClintock, W., Barth, C., and Sandel, B. 1998b. Galileo Orbiter

ultraviolet

observations of Jupiter aurora. J. Geophys. Res. 103: 20125–20148.

Ajello,

J., Shemansky, D. E., Pryor, W., Stewart, A. I., Simmons, K., Majeed, T., Waite, H., and Gladstone,G.

2001. Spectroscopic evidence for high altitude aurora from Galileo extreme ultraviolet and Hopkins

ultraviolet

telescope observations. Icarus 152: 151–171.

Ajello,

J., Vatti Palle, V. P., and Osinski, G. 2002a. UV spectroscopy by electron impact for planetary astronomy

and astrophysics. In Current Developments in Atomic, Molecular Physics, M. Mohan (ed.), pp. 143–150.

NewYork:

Kluwer

Academic

Press.

Ajello,

J. M., Hansen, D., Beegle, L. W., Terrell, C., Kanik, I., James, G., and Makarov, O. 2002b. The mid-

dle ultraviolet and visible spectrum of SO

by electron impact. J. Geophys. Res. 107: SIA2.1–SIA2.7,

doi:10.1029/2001JA000122.

Ajello, J., Pryor, W., Esposito, L., Stewart, I., McClintock, W., Gustin, J., Grodent, D., Gérard, J.-C., and

Clarke, J. 2005a. The Cassini Campaign observations of the Jupiter aurora by the ultraviolet imaging

spectrograph

and the space telescope imaging spectrograph. Icarus 178: 327–345.

Ajello,

J., Vatti Palle, P., Abgrall, H., Roueff, E., Bhardwaj, A., and Gustin, G. 2005b. The electron excited UV

spectrum

of HD: Cross sections and transition probabilities. Astrophys. J. Suppl. 159: 314–330.

Ajello,

J. M., Stevens, M. H., Stewart, I., Larsen, K., Esposito, L., Colwell, J., Mcclintock, W., Holsclaw, G.,

Gustin, J., and Pryor, W. 2007. Titan airglow spectra from Cassini ultraviolet imaging spectrograph

(UVIS):

EUV analysis. Geophys. Res. Lett. 34: L24204, doi:10.1029/2007GL031555.

Ajello,

J. M., Aguilar, A., Mangina, R. S., James, G. K., Geissler, P., and Trafton, L. 2008. The mid-

dle UV to near IR spectrum of electron excited SO

. J. Geophys. Res.-Planets 113: E03002,

doi:10.1029/2007je002921.

UV Molecular Spectroscopy from Electron Impact for Astrophysics 799

Avakyan, S. V., Ii’In, R. N., Lavrov, V. M., and Ogurstov, G. N. 1998. Collision Processes and Excitation of UV

Emission from Planetary Atmospheric Gases: A Handbook of Cross Sections, pp. 1–342. Amsterdam, the

Netherlands:

Gordon and Breach Science Publishers.

Bagenal,

F., Dowling, T., and McKinnon, W. 2007. Jupiter, The Planet, Satellites and Magnetosphere

(Cambridge Planetary Science),

pp. 1–684. Cambridge, U.K.: Cambridge University Press.

Ballester,

G. E., Clarke, J. T., Rego, D., Combi, M., Larsen, N., Ajello, J., Strobel, D. F., Schneider, N. M.,

and McGrath, M. 1996. Characteristics of Io’s far-UV neutral oxygen and sulfur emissions derived from

recent

HST observations. Bull. Am. Astron. Soc. 28: p1156.

Ballester,

G. E. 1998. Ultraviolet Astrophysics Beyond the IUE Final Archive, pp. 21–28. Noordwijk, the

Netherlands:

ESA Publications.

Barth,

C. A., Stewart, A. I. F., and Brougher, S. W. 1992. Mars, pp. 1054–1065. Tucson, AZ: University of

Arizona

Press.

Beegle,

L., Ajello, J. M., James, G. K., Dziczek, D., and Alvarez, M. 1999. The emission spectrum of the CO

Π-X

) fourth positive system by electron impact. Astron. Astrophys. 347: 375–390.

Bergin, E., Calvet, N., Sitko, M. L., Abgrall, H., D’Alessio, P., Herczeg, G. J., Roueff, E., Qi, C., Lynch, D. K.,

Russell, R. W., Brafford, S. M., and Perry, R. B. 2004. New probe of planet forming region in T Tauri

Disks.

Astrophys. J. 614: L133–136.

Bishop,

J. and Feldman, P. 2003. Analysis of the Astro-1/Hopkins Ultraviolet Telescope EUV-FUV dayside

nadir

spectral radiance measurements. J. Geophys. Res. 108: 1243, doi:10.1029/2001JA000330.

Bouchez,

A. H., Brown, M. E., and Schneider, N. 2000. Eclipse spectroscopy of Io’s atmosphere. Icarus 148:

316–319.

Brinkmann, R. T. and Trajmar, S. 1970. Electron impact excitation of N

. Annales de Geophysique 26: 201–207.

Broadfoot, A. L., Belton, M. J. S., Takacs, P. J., Sandel, B. R., Shemansky, E. E., Holberg, J. B., Ajello, J. M.,

Atreya, S. K., Donahue, T. M., Moos, H. W., Bertaux, J. L., Blamont, J. E., Strobel, D. F., McConnell, J. C.,

Dalgarno, A., Goody, R., and McElroy, M. B. 1979. Extreme ultraviolet observations from Voyager 1

encounter

with Jupiter. Science 204: 979–982.

Broadfoot,

A. L., Sandel, B. R., Shemansky, D. E., McConnell, J. C., Smith, G. R., Holberg, J. B., Atreya, S. K.,

Donahue, T. M., Strobel, D. F., and Bertaux, J. L. 1981a. Overview of the Voyager ultraviolet spectrom-

etry

results through Jupiter encounter. J. Geophys. Res. 86: 8259–8284.

Broadfoot,

A. L., Sandel, B. R., Shemansky, D. E., Holberg, J. B., Smith, G. R., Strobel, D. F., McConnell, J. C.,

Kumar, S., Hunten, D. M., Atreya, S. K., Donahue, T. M., Moos, H. W., Bertaux, J. L., Blamont, J. E.,

Pomphrey, R. B., and Linick, S. 1981b. Extreme UV observations from Voyager 1 encounter of Saturn.

Science

212: 206–211.

Broadfoot,

L.,

Atreya,

S. K., Bertaux, J. L., Blamont, J. E., Dessler,

J., Donahue, T. M., Forrester, W. T.,

Hall,D. T., Herbert, F., Holberg, J. B., Hunten, D. M., Krasnopolsky, V. A., Linick, S., Lunine, J. I.,

Mcconnell, J. C., Moos, H. W., Sandel, B. R., Schneider, N. M., Shemansky, D. E., Smith, G. R., Strobel,

D. F., and Yelle, R. V. 1989. Ultraviolet spectrometer observations of Neptune and Triton. Science 246:

1459–1466.

Brunger, M. J. and Teubner, P. J. O. 1990. Differential cross sections for electron-impact excitation of the elec-

tronic

states of N

source. Phys. Rev. A 41: 1413–1426.

Bunce, E. J. and Cowley, S. W. H. 2001. Divergence of the equatorial current in the dawn sector of Jupiter’s

magnetosphere: Analysis of Pioneer and Voyager magnetic eld data. Planet. Space Sci. 49: 1089–1113.

Budzien, S. A., Feldman, P. D., and Conway, R. R. 1994. Observations of the far ultraviolet airglow by the

ultraviolet

limb imaging experiment on STS-39. J. Geophys. Res. 99: 23275–23287.

Campbell,

L., Brunger, M. J., Nolan, A. M., Kelly, L. J., Wedding, A. B., Harrison, J., Teubner, P. J. O.,

Cartwright, D. C., and McLaughlin, B. 2001. Integral cross sections for electron impact excitation of

electronic

states of N

. J. Phys. B 34: 1185–1199.

Cartwright, D. C. 1978. Vibrational populations of the excited states of N

under auroral conditions. J. Geophys.

Res.

83: 517–531.

Cartwright,

D. C., Chutjian, A., Trajmar, S., and Williams, W. 1977. Electron-impact excitation of elec-

tronic states of N

: 1. Differential cross-sections at incident energies from 10 to 50 eV. Phys. Rev. A 16:

1013–1040.

Ciocca, M., Ajello, J. M., Liu, X., and Maki, J. 1997a. Kinetic energy distribution of D(2p) atoms from analysis

the D Lyman- α line prole. Phys. Rev. A 56: 1929–1937.

Ciocca,

M., Kanik, I., and Ajello, J. M. 1997b. High resolution studies extreme ultraviolet emission from CO.

Phys. Rev. A

55: 3547–3556.

Clarke,

J. T., Ajello, J., Luhmann, J., Scheider, N., and Kanik, I. 1994. HST UV spectral observations of io

passing

into eclipse. J. Geophys. Res. 99: 8387–8402.