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Title: Ionization of low-Rydberg-state He atoms by polar molecules. II. Large rotational-energy transfers and absolute values of the cross sections

Abstract

The absolute values of cross sections for the collisional ionization of low-Rydberg-state He atoms in the n /sup 1/P state (n = 14) by the polar molecules NH/sub 3/, SO/sub 2/, and acetone (C/sub 3/H/sub 6/O) are measured in a crossed-beam experiment at thermal kinetic energies, for a well-defined relative velocity. Simultaneous Penning ionization of NH/sub 3/ by metastable He(2/sup 3/S) atoms is carried out in situ for calibration. Experimental collisional-ionization cross sections sigma/sub i//sup expt/(v/sub r/), for v/sub r/ = 2400 m/s, as large as 9 x 10/sup -15/ cm/sup 2/ for NH/sub 3/, 5 x 10/sup -15/ cm/sup 2/ for SO/sub 2/, and 10/sup -14/ cm/sup 2/ for C/sub 3/H/sub 6/O at 300 K, are obtained. These large cross sections cannot be explained by the ''free-electron model'' usually used in Rydberg-atom--molecule collisions: This model predicts no ionization of Rydberg levels as low as n = 14, since the amount of energy available from rotational ..delta..J = -1 ..delta..K = 0 relaxation transitions of the molecule is insufficient. Our hypothesis of large /vert bar/..delta..J/vert bar/ rotational transitions is strengthened by comparison of the results for the three studied molecules.

Authors:
; ; ;
Publication Date:
Research Org.:
Service de Physique des Atomes et des Surfaces, Centre d'Etudes Nucleaires de Saclay, 91191 Gif-sur-Yvette Cedex, France
OSTI Identifier:
6682335
Resource Type:
Journal Article
Journal Name:
Phys. Rev. A; (United States)
Additional Journal Information:
Journal Volume: 38:9
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; HELIUM; ATOM-MOLECULE COLLISIONS; ENERGY TRANSFER; IONIZATION; RYDBERG STATES; POLAR COMPOUNDS; ROTATIONAL STATES; ACETONE; AMMONIA; CALIBRATION; COLLIDING BEAMS; CROSS SECTIONS; METASTABLE STATES; PENNING EFFECT; ATOM COLLISIONS; BEAMS; COLLISIONS; ELEMENTS; ENERGY LEVELS; EXCITED STATES; FLUIDS; GASES; HYDRIDES; HYDROGEN COMPOUNDS; KETONES; MOLECULE COLLISIONS; NITROGEN COMPOUNDS; NITROGEN HYDRIDES; NONMETALS; ORGANIC COMPOUNDS; RARE GASES; 640304* - Atomic, Molecular & Chemical Physics- Collision Phenomena

Citation Formats

Pesnelle, A, Ronge, C, Perdrix, M, and Watel, G. Ionization of low-Rydberg-state He atoms by polar molecules. II. Large rotational-energy transfers and absolute values of the cross sections. United States: N. p., 1988. Web. doi:10.1103/PhysRevA.38.4560.
Pesnelle, A, Ronge, C, Perdrix, M, & Watel, G. Ionization of low-Rydberg-state He atoms by polar molecules. II. Large rotational-energy transfers and absolute values of the cross sections. United States. https://doi.org/10.1103/PhysRevA.38.4560
Pesnelle, A, Ronge, C, Perdrix, M, and Watel, G. Tue . "Ionization of low-Rydberg-state He atoms by polar molecules. II. Large rotational-energy transfers and absolute values of the cross sections". United States. https://doi.org/10.1103/PhysRevA.38.4560.
@article{osti_6682335,
title = {Ionization of low-Rydberg-state He atoms by polar molecules. II. Large rotational-energy transfers and absolute values of the cross sections},
author = {Pesnelle, A and Ronge, C and Perdrix, M and Watel, G},
abstractNote = {The absolute values of cross sections for the collisional ionization of low-Rydberg-state He atoms in the n /sup 1/P state (n = 14) by the polar molecules NH/sub 3/, SO/sub 2/, and acetone (C/sub 3/H/sub 6/O) are measured in a crossed-beam experiment at thermal kinetic energies, for a well-defined relative velocity. Simultaneous Penning ionization of NH/sub 3/ by metastable He(2/sup 3/S) atoms is carried out in situ for calibration. Experimental collisional-ionization cross sections sigma/sub i//sup expt/(v/sub r/), for v/sub r/ = 2400 m/s, as large as 9 x 10/sup -15/ cm/sup 2/ for NH/sub 3/, 5 x 10/sup -15/ cm/sup 2/ for SO/sub 2/, and 10/sup -14/ cm/sup 2/ for C/sub 3/H/sub 6/O at 300 K, are obtained. These large cross sections cannot be explained by the ''free-electron model'' usually used in Rydberg-atom--molecule collisions: This model predicts no ionization of Rydberg levels as low as n = 14, since the amount of energy available from rotational ..delta..J = -1 ..delta..K = 0 relaxation transitions of the molecule is insufficient. Our hypothesis of large /vert bar/..delta..J/vert bar/ rotational transitions is strengthened by comparison of the results for the three studied molecules.},
doi = {10.1103/PhysRevA.38.4560},
url = {https://www.osti.gov/biblio/6682335}, journal = {Phys. Rev. A; (United States)},
number = ,
volume = 38:9,
place = {United States},
year = {1988},
month = {11}
}