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Studies of extreme-ultraviolet emission from Rydberg series of H_2 by electron impact

Ajello, J. M. and Shemansky, D. and Kwok, T. L. and Yung, Y. L. (1984) Studies of extreme-ultraviolet emission from Rydberg series of H_2 by electron impact. Physical Review A, 29 (2). pp. 636-653. ISSN 1050-2947. https://resolver.caltech.edu/CaltechAUTHORS:20140910-155006837

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Abstract

Electron excitation cross sections have been measured for the following two Rydberg series of H_2: ^1Σ_u^+ 1sσnpσ (B, B′, and B", states with principal quantum numbers n=2, 3, and 4, respectively) and ^1Π_u 1sσnpπ (C, D, and D′ states with principal quantum numbers n=2, 3, and 4, respectively) over the energy range from threshold to 350 eV. The cross sections for these six states account for all (>99%) of the vacuum-ultraviolet emission (78-170 nm) of the singlet states of H_2. The estimated total direct-excitation cross sections for these six states at 100 eV in decreasing value are (4.02±0.60)×10^(−17) cm^2 for B^1Σ_u^+ (3.86±0.60)×10^(−17) cm^2 for C^1Π_u, (0.76±0.11)×10^(−17) cm^2 for D^1Π_u, (0.76±0.11)×10^(−17) cm^2 for B' ^1Σ_u^+, (0.30±0.06)×10^(−17) cm^2 for D′^1Π_u, and (0.23±0.05)×10^(−17) cm^2 for B"^1Σ_u^+ and, additionally, (0.43±0.10)×10^(−17) cm^2 for E,F^1Σ_g^+ which populates the B^1Σ_u^+ state through radiative cascade transitions. We estimate the predissociation (autoionization is weak) and emission yields of the vibrational levels of the D, D′, and B" states whose band systems exhibit strong "breaking off in emission" for wavelengths below 85 nm. Furthermore, we report the first direct measurement of the dissociative excitation cross section for production of Lyman-β of (8.9±3.0)×10^(−19) cm^2 at 100 eV. In particular, it is shown that the high-lying Rydberg states (n=3 and 4) make a substantial contribution to the observed emission below 110 nm while above 110 nm the Lyman bands (B^1Σ_u^+→X^1Σ_g^+) and Werner bands (C^1Π_u→X^1Σ_g^+), the first members of the Rydberg series, dominate the spectrum. As a result of these measurements and spectroscopic models the ultraviolet (UV) spectrum from H_2 by electron impact can serve as an intensity calibration standard from 80 to 170 nm.


Item Type:Article
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http://dx.doi.org/10.1103/PhysRevA.29.636DOIArticle
http://journals.aps.org/pra/abstract/10.1103/PhysRevA.29.636PublisherArticle
Alternate Title:Studies of extreme-ultraviolet emission from Rydberg series of H2 by electron impact
Additional Information:© 1984 The American Physical Society. Received 19 May 1983. Published in the issue dated February 1984. The authors thank J. A. R. Samson for interesting discussions of polarization, S. K. Srivastava for the electron gun design, and E. C. Zipf for valuable discussions. The authors also wish to thank M. Glass-Maujean and J. Y. Roncin for valuable discussions and for communicating unpublished data. This work was supported by the U.S. Air Force Office of Scientific Research (AFOSR) Planetary Atmospheres and Astronomy/Relativity Programs of National Aeronautics and Space Administration (NASA). It represents one phase of work sponsored by NASA under Contract No. NAS7-100 to the Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109. This work was also supported by NASA, Division of Planetary Sciences Grant No. NAGW-106.
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Funding AgencyGrant Number
Air Force Office of Scientific Research (AFOSR)UNSPECIFIED
NASANAS7-100
NASANAGW-106
Issue or Number:2
Record Number:CaltechAUTHORS:20140910-155006837
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20140910-155006837
Official Citation:Studies of extreme-ultraviolet emission from Rydberg series of H2 by electron impact J. M. Ajello, D. Shemansky, T. L. Kwok, and Y. L. Yung Phys. Rev. A 29, 636 (1984) – Published 1 February 1984
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49566
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:11 Sep 2014 16:15
Last Modified:03 Oct 2019 07:15

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