Eur. Phys. J. D (2016) 70: 100
https://doi.org/10.1140/epjd/e2016-70085-9

Regular Article

Change in resonance parameters of a linear molecule as it bends: Evidence in electron-impact vibrational transitions of hot COS and CO₂ molecules^*

¹ Department of Physics, Sophia University, Chiyoda-ku, 102-8554 Tokyo, Japan
² Fine Chemicals Sales Dept.-III, Sales Div., Kanto Denka Kogyo Co., Ltd., Chiyoda-ku, 101-0063 Tokyo, Japan
³ Development & Marketing Management Dept., New Products Development Div., Kanto Denka Kogyo Co., Ltd., Chiyoda-ku, 101-0063 Tokyo, Japan
⁴ Shibukawa Decelopment Research Lab., New Products Development Div., Kanto Denka Kogyo Co., Ltd., Shibukawa-shi, 377-0008 Gunma, Japan
⁵ Laboratório de Colisões Atómicas e Moleculares, CEFITEC, Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
⁶ Atomic Physics Research Unit, RIKEN, Hirosawa 2-1, Wako, 351-0198 Saitama, Japan

^a e-mail: masami-h@sophia.ac.jp

Received: 8 February 2016
Received in final form: 14 March 2016
Published online: 3 May 2016

Abstract

Inelastic and superelastic electron-impact vibrational excitation functions of hot carbonyl sulphide COS (and hot CO₂) are measured for electron energies from 0.5 to 3.0 eV (1.5 to 6.0 eV) and at a scattering angle of 90°. Based on the vibrational populations and the principle of detailed balance, these excitation functions are decomposed into contributions from state-to-state vibrational transitions involving up to the second bending overtone (030) in the electronically ground state. Both the ²Π resonance for COS around 1.2 eV and the ²Π_u resonance for CO₂ around 3.8 eV are shifted to lower energies as the initial vibrational state is excited in the bending mode. The width of the resonance hump for COS changes only little as the molecule bends, whereas that of the overall boomerang resonance for CO₂ becomes narrower. The angular distribution of the electrons resonantly scattered by hot COS and hot CO₂ is also measured. The different shapes depending on the vibrational transitions and gas temperatures are discussed in terms of the symmetry of the vibrational wave functions.