On the vibrational state dependence of the asymmetry parameter of angular distribution in the photoelectron spectra

Abstract

A discussion is given on the changes obtainable in the asymmetry parameter fl with vibrational state of the ion in the approximation involving fixed direction of body-frame orientation during the electron ejection. The R dependence of the electronic matrix elements is taken into account by calculation of appropriate displaced oscillator integrals. Inclusion of a nuclear matrix element gives in most cases negligible effect for the direct ionization.fly" are calculated for H2 and N2. Expected variations in fly" are compared with recent experimental data on N2 and CO. Higher partial waves and their effect on fly' are discussed.

Vibrational State Dependence of the Photoelectron Angular Asymmetry Parameter caused by Vibronic Coupling

“…on the vibrational state is unexpected within the Born-Oppenheimer approximation, where the total wave function is factorized into an electronic component (independent of the nuclear coordinates) and a nuclear component. Ritchie [7] and Kalman [8] showed that for diatomic molecules a dependence of the electronic transition moment on the internuclear distance leads to a vibrational state dependence of 0. A further mechanism, which may cause a drastic variation of p within the vibrational envelope of a band, is autoionization.…”

On the coupling in the final state in the photoelectron spectra

“…and Xn,,., do not come from the same set; they correspond to different r~ and v values. Therefore, even without an R dependence for Jn~,(t '), there may be coupling, The extent of this will vary with the ratio v'/v and difference ~e-re (see [18] for a method of calculation) and the selection rules for undisplaced harmonic oscillators no longer hold.…”

Photoelectron angular distributions from H2 and D2

“…Several theoretical calculations of a(H 2 ) have been published [4][5][6][7][8][9][10][11][12][13][14][15][16][17], and a number of groups have measured a(H 2 ) using discrete resonance line radiation [18][19][20][21][22][23][24]. Recently, Marr et al [25] reported measurements over the photon energy range 18-30 eV using synchrotron radiation.…”