Dependence of electron-impact dissociative excitation cross sections on the initial vibrational quantum number inH2andD

Abstract

Electron-impact dissociative cross sections for H2 and D2 vibrationally excited molecules have been calculated in the frame of the impact-parameter method for dissociative processes involving direct dissociation M2(X'Xg, U;)+e~M2(B 'X"+, C'H")+e~2M+e and radiative cascade M2(X'Xg, v;) +e~Mz (B 'X"+, C'll")+e -+M2(X 'Xg+)+e+hv~2M+e+hv (M2 represents a hydrogen or deuterium molecule). The results show that direct dissociation cross sections strongly depend on the initial vibrational state of the molecule, while an opposite behavior is found in the case of dissociation by radiative cascade. Moreover, for this last process, the fraction of molecules that undergoes dissociation has been evaluated with respect to the total cascade process, yielding in general quite small values in both the H2 and D2 cases.PACS number(s): 34.80.Gs, 52.20.Fs

Cross Section Data for Electron-Impact Inelastic Processes of Vibrationally Excited Molecules of Hydrogen and Its Isotopes

“…Vibrational and dissociative excitation cross sections for this two-step process have been obtained for both H 2 and D 2 molecules [12,13], including in the electron-impact excitation step (leading to H * …”

“…In the present paper the following singlet-singlet (optically allowed) transitions have been included: g , except the last one which involves two excited electronic states. The related dissociative and total cross sections (the bound-to-bound non-dissociative cross sections can be obtained from (2.1) by subtraction) have been calculated as a function of both the incident energy and the initial vibrational quantum number v i , by using the quantum-mechanical impact parameter method [5,7,8,13,19,20].…”

“…[10][11], -excitation-radiative decay processes: Refs. [12][13], -dissociative electron attachment: Refs. [4,14].…”

Dissociative excitation of selenium atoms in collisions of electrons with Se2 molecules

“…In the experiment of [22], the temperature was much lower, and the fraction of Se 2 molecules in the beam was very small. It is known [25,26] that the cross sections of electron-molecule collisions including dissociative excitation depend significantly on the vibrational level of ground electron state on which the molecule finds itself prior to collision with electron. Celiberto et al [26] demonstrated that the dissociative excitation cross sections in collisions of electrons with H 2 and D 2 molecules for excitation from the initial levels with vibrational quantum numbers v′ = 0 and v′ = 3, 4 differ by almost an order of magnitude.…”

“…It is known [25,26] that the cross sections of electron-molecule collisions including dissociative excitation depend significantly on the vibrational level of ground electron state on which the molecule finds itself prior to collision with electron. Celiberto et al [26] demonstrated that the dissociative excitation cross sections in collisions of electrons with H 2 and D 2 molecules for excitation from the initial levels with vibrational quantum numbers v′ = 0 and v′ = 3, 4 differ by almost an order of magnitude. In the present-day experiments aimed at studying electron-molecule collisions, it is still impossible to realize molecular beams selected by vibrational quantum numbers of the initial state (the more so, beams of large extent).…”