Junichi Kurawaki

Translational energy distribution and production mechanism of excited hydrogen atoms produced in electron-CH4 collisions

Abstract The Balmer-β line of the excited hydrogen atom ( n = 4) produced in e-CH 4 collisions has been measured at a resolution of about 0.03 A and at angles of 55° and 90° with respect to the electron beam. The translational energy distribution of H* calculated from the line shape has at least three components; the peaks in the translational energy with their threshold energies in parentheses are 3 eV (21.6 ± 0.5 eV), 0–1 eV (28.1 ± 1.0 eV) and 4 eV (35.3 ± 1.5 eV). There seems to be a fourth peak with a translational energy of about 8–12 eV. Excitation to the Rydberg states converging to the Ā 2 A 1 state of CH 4 + is the major process for the formation of the first component. Optically-forbidde doubly excited states play important roles in the formation of the other components.

Translational energy distribution and production mechanism of H* and D* produced by controlled electron impact on water and heavy water

The high resolution spectra of the Balmer lines of H* (n=3,4) and D* (n=3,4) have been measured with the use of a Fabry–Perot interferometer. Translational energy distributions of H* and D* calculated from their Doppler profiles have four components; their peaks lie at about 0.5, 4, 2, and 6–8 eV. There are four thresholds for the formation of H* (n=4) and D* (n=4) at about 18.7, 25.5, 31.3, and 38.9 eV. The production mechanisms of these components have been assigned to dissociation through Rydberg states converging to some ionic states of water such as the B 2B2, 2B1, 2A1, and doubly ionized states, respectively.

Translational energy distributions and production mechanisms of the excited hydrogen atom (n = 3,4) produced in e-NH3 collisions

The Balmer α and β lines produced in e-NH3 collisions have been measured precisely with the use of a Fabry-Perot interferometer. These lines are not polarized. The translational energy distributions of (H*(n = 3,4) were determined from analysis of Doppler lineshapes and have five components; their peaks lie at 1, 3, 2, 4–5 and 8–12 eV. The excitation function [H*(n = 4)] has five thresholds at 22.5, 29.0, 33.3, 38.9 and 41.7 eV, and indicates that five dissociation processes contribute to the formation of H*. Excitation to the Rydberg states converging to the (2a1)−1 state of NH3+ is a major process for the formation of the first and the second components. Doubly excited Rydberg states play important roles in the dissociative excitation of NH3.

Translational energy distributions of the excited nitrogen atom produced by electron-impact dissociative excitation of nitrogen molecules

The Doppler line shapes of atomic nitrogen emission (4p 2S1/2–3s 2P3/2: 4935.12 A) were measured precisely with a Fabry–Perot interferometer at a resolution of 0.015 A. The translational energy distributions of N* were calculated and found to be similar with those of N+ and N(HR). There are three major components of N*; their peaks of the translational energy distribution and threshold energies are (1) 0.1–1.3 and 23.0 eV, (2) 2.8–3.0 and 29 eV, and (3) ∼ 5 and 38–44 eV, respectively. The first component is produced by dissociative excitation through Rydberg states converging to the C state of N2+.

Absolute emission cross section of the slow component of exicted hydrogen atoms produced in e—H2O collisions

Abstract The translational energy distribution of H*(n = 4) arising from e—H2O collisions has been measured. The absolute cross section for the process leading to the slowest component has been estimated in the energy range 25–300 eV and is comparied with theoretical predictions.

Angular distributions of the slow and fast groups of excited hydrogen atom produced in e-H2 collisions

Abstract The angular dependence has been investigated for the slow and the fast groups of H*( n = 4) resulting from H 2 dissociative electron impact. The slow group is isotropic due to coexistence of several processes and/or effects of predissociation. The fast group shows a sin 2 θ dependence and is produced mainly through Rydberg states of II u symmetry.

Isotope effects in the emission cross section of H* and D* produced by controlled electron impact on H2O and D2O

Abstract The dynamics of the dissociation of water has been investigated by measuring the intensity of the Balmer lines. The isotope effects on the emission cross section depend on the incident electron energy and the principal quantum number of the excited hydrogen atom. Furthermore, the Balmer-α, -β, -γ lines taken at high resolution have been divided into a slow and a fast group of excited hydrogen atoms ( n = 3, 4, 5). The isotope effects for the slow group are 0.78 ± 0.09, 0.71 ± 0.08 and 0.70 ± 0.05, and those for the fast group are 0.97 ± 0.11, 0.94 ± 0.07 and 0.89 ± 0.05 for n = 3, 4 and 5, respectively; these values are independent of the electron energy. Absolute emission cross sections for the slow and the fast groups were also evaluated; those of the slow group have a maximum at = 70 eV and those of the fast group at = 100 eV.

Translational-Energy-Dependent Emission Cross Sections of Excited Hydrogen Atoms Produced in Electron-Methane, Ethane, Ethylene and Acetylene Collisions

Translational-energy dependence of emission cross sections was measured for H* (n=4) produced in collisions of methane, ethane, ethylene and acetylene with electrons through analysis of Doppler profiles of the Balmer-β line. Emission cross sections were calculated for the translational energies of 0-2, 2-4, 4-6, 6-8 and >8 eV. The translational-energy dependences of emission cross sections are similar for the four hydrocarbons. The five segments can be classified into 3 groups. The first group, 0-2 eV, is dominant at lower electron energies. The second group, 2-4 and 4-6 eV, is dominant above 40 eV. The third group, 6-8 and >8 eV, has some contribution at higher electron energies.