Morihide Higo

Analysis of the translational energy distribution of H* produced in the eH2 collision

Abstract The translational energy distribution of an emissive fragment can be obtained by differentiating the Doppler line shape of its emission line. This distribution of H* produced by electron impact on H 2 shows two prominent peaks and indicates the importance of the dissociative excitation through the molecular Rydberg states.

Translational energy distribution and production mechanism of excited hydrogen atoms produced by controlled electron impact on H2

Abstract The Balmer-β line of the excited hydrogen atom ( n = 4) (H*) produced in e—H 2 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* has been calculated from an analysis of the line shape. Three major components appear and their peaks lie at about 0, 4 and 8 eV. The excitation function of H* is found to have three thresholds at 17.1, 24 and 27 eV. These results show that there are three major processes for the formation of H*: dissociation through the (1sσ g )(4l) states of H 2 and predissociation through relevant Rydberg states for the 0 eV component; dissociation mainly through the (2pσ u ) 2 state for the 4 eV component; and dissociation mainly through the (2pσ u (4l) states for the 8 eV component.

Translational energy distribution of the excited hydrogen atom produced by controlled electron impact on HCl

Abstract The translational energy distribution of an atom can be calculated by differentiating the Doppler line shape of its emission line taken at a high optical resolution. The Balmer-β line of the excited hydrogen atom ( n = 4) produced by electron impact on HCl has been measured at a high resolution (0.033A) and at two angles (55° and 90°) with respect to the electron beam. The translation energy distribution depends on the electron energies and has almost two groups of components: ≈ 5 eV (fast) and ≈ eV (slow). Anisotropy is imporant for the slow component. The excitation function shows the corresponding structures. It is concluded that Rydberg states converging to the 2 Π state of HCl + produce the fast component and Rydberg states converging to the repulsive HCl + states which cross the 2 Σ + state produce the slow component.

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 Bu20092B2, 2B1, 2A1, and doubly ionized states, respectively.

Translational energy distribution of excited deuterium atoms produced by controlled electron impact on D2

Abstract The Balmer-β line of the excited deuterium atom [D*(n = 4)] produced in e—D2 collisions has been measured at high resolution (0.029–0.033 A) and at various electron energies (17–100 eV). The translational energy distribution of D*(n = 4) has been calculated from analysis of its Doppler line shape. The distribution of D* has three major components as in the case of H*(n = 4) from H2 reported in our previous paper. Their peaks lie at about 0, 6 and 8 eV. The excitation function of D* is found to have two thresholds at 17.4 and 26.4 eV. The second component of D* has a larger translational energy and a higher threshold than those of the corresponding component of H*. These results indicate that the contribution from the lowest doubly excited state, 1Σg+(2pσu)2, is much smaller for D2 than that for H2.

Isotope effects for the formation of slow and fast excited hydrogen atoms produced by controlled electron impact on H2 and D2

Abstract Analysis of the Balmer-β line taken at high resolution clarifies the isotope effect in the dissociative excitation of H 2 . The isotope effect is larger for slow H ∗ atoms (σ D /σ H = 0.4–0.6) than for fast H ∗ atoms and has almost no electron energy dependence (25–100 eV).