SPECTRA, EMISSION YIELDS, CROSS SECTIONS, AND KINETIC ENERGY DISTRIBUTIONS OF HYDROGEN ATOMS FROM H2 X 1Σg+- d 3Πu EXCITATION BY ELECTRON IMPACT

被引：5

作者：

Liu, Xianming ^{[1
]}

Shemansky, Donald E. ^{[1
]}

Yoshii, Jean ^{[1
]}

Johnson, Paul V. ^{[2
]}

Malone, Charles P. ^{[2
]}

Ajello, Joseph M. ^{[3
]}

机构：

[1] Space Environm Technol, Planetary & Space Sci Div, Pacific Palisades, CA 90272 USA

[2] CALTECH, Jet Prop Lab, 4800 Oak Grove Dr, Pasadena, CA 91109 USA

[3] Univ Colorado, Lab Atmosphere & Space Phys, Boulder, CO 80303 USA

来源：

ASTROPHYSICAL JOURNAL | 2016年 / 818卷 / 02期

基金：

美国国家科学基金会; 美国国家航空航天局;

关键词：

molecular data; molecular processes; QUANTUM-DEFECT THEORY; INFRARED-LASER SPECTROSCOPY; ANGULAR-MOMENTUM STATES; TRIPLET GERADE COMPLEX; AB-INITIO CALCULATION; MOLECULAR-HYDROGEN; HIGH-RESOLUTION; FINE-STRUCTURE; TRANSITION MOMENTS; DISSOCIATIVE DECAY;

D O I：

10.3847/0004-637X/818/2/120

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Electron-impact excitation of H2 triplet states plays an important role in the heating of outer planet upper thermospheres. The d (3)Pi(u) state is the third ungerade triplet state, and the d (3)Pi(u)-a (3)Sigma(+)(g) emission is the largest cascade channel for the a (3)Sigma(+)(g) state. Accurate energies of the d (3)Pi(-)(u)(v, J) levels are calculated from an ab initio potential energy curve. Radiative lifetimes of the d (3)Pi(u)(v, J) levels are obtained by an accurate evaluation of the d (3)Pi(u)-a (3)Sigma(+)(g) transition probabilities. The emission yields are determined from experimental lifetimes and calculated radiative lifetimes and are further verified by comparing experimental and synthetic d (3)Pi(u)-a (3)Sigma(+)(g) spectra at 20 eV impact energy. Spectral analysis revealed that multipolar components beyond the dipolar term are required to model the X (1)Sigma(+)(g)-d (3)Pi(u) excitation, and significant cascade excitation occurs at the d (3)Pi(u)(v = 0,1) levels. Kinetic energy (E-k) distributions of H atoms produced via predissociation of the d (3)Pi(u) state and the d (3)Pi(u)-a (3)Sigma(+)(g)-b (3)Sigma u(+) cascade dissociative emission are obtained. Predissociation of the d (3)Pi(u) state produces H atoms with an average E-k of 2.3 +/- 0.4 eV/atom, while the E-k distribution of the d (3)Pi(u)-a (3)Sigma(+)(g)-b (3)Sigma(+)(u) channel is similar to that of the X (1)Sigma(+)(g)-a (3)Sigma(+)(g)-b (3)Sigma(+)(u) channel and produces H(1s) atoms with an average E-k of 1.15 +/- 0.05 eV/atom. On average, each H-2 excited to the d (3)Pi(u) state in an H-2-dominated atmosphere deposits 3.3 +/- 0.4 eV into the atmosphere, while each H-2 directly excited to the a (3)Sigma(+)(g) state gives 2.2-2.3 eV to the atmosphere. The spectral distribution of the calculated a (3)Sigma(+)(g)-b (3)Sigma(+)(u) continuum emission due to the X (1)Sigma(+)(g)-d (3)Pi(u) excitation is significantly different from that of direct a (3)Sigma(+)(g) excitation.

引用

页数：17

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