Interplay of different partial waves on vibrationally resolved photoionization of the OKshell of the CO molecule

Abstract

The asymmetry parameter ␤ for the O K shell photoemission of the CO molecule has been measured for different vibrational states of the residual ion. The corresponding calculations performed by us in the relaxed core Hartree-Fock approximation are in qualitative agreement with the experiment. From the analysis of theoretical data, we made the conclusion that the variation of ␤ with the vibrational quantum number is connected with different dependences of the dipole matrix elements in the s, d, and f channels on the internuclear distance R in the * shape resonance.

Vibrational branching ratios in the photoelectron spectra of N2 and CO: interference and diffraction effects

“…At higher energies the RCHF approximation has also been used (CO 43,44,50,52,54,67,[115][116][117][118][119][120] , N 2 3 ). This is in contrast with the frozen core Hartree Fock (FCHF) approximation, which has widely been used in most earlier and some recent works (CO 42,48,58,74,75,106,121 , N 2 22,27,32,58,74,75,106 ).…”

“…Only a few methods described in the previous section have been used to study vibrationally resolved photoionization of CO 13,43,50,52,54,55,58,[65][66][67][68]78 and N 2 13,30,35,58,60,61,63,64,69-71,78 , and almost none in the region of high photon energies 78 . The reason is that one has to evaluate electronic continuum wave functions and potential energy curves in a dense grid of internuclear distances, which makes most methods prohibitively expensive.…”

“…In particular, a wealth of experimental and theoretical data has been published for total cross sections corresponding to core as well as valence-shell photoionization of the prototype N 2 1-35 and CO 1,2,5,6,12,13,34,[36][37][38][39][40][41][42][43][44][45][46][47][48][49] molecules, from the ionization threshold up to a few tens of eV above it. More recently, the advent of high-brilliance 3rd-generation synchrotron radiation sources in combination with high energy-resolution detection techniques has opened the way for the determination of vibrationally resolved photoionization spectra of these molecules, both at low and high photon energies 30,35,38,39,[50][51][52][53][54][55][56][57][58][59][60][61][62][63][64] . These experimental achievements have fostered the development of new theoretical methods that, in addition to accounting for electronic degrees of freedom, are also able to describe the molecule's vibrations 13,30,35,…”

“…More recently, the advent of high-brilliance 3rd-generation synchrotron radiation sources in combination with high energy-resolution detection techniques has opened the way for the determination of vibrationally resolved photoionization spectra of these molecules, both at low and high photon energies 30,35,38,39,[50][51][52][53][54][55][56][57][58][59][60][61][62][63][64] . These experimental achievements have fostered the development of new theoretical methods that, in addition to accounting for electronic degrees of freedom, are also able to describe the molecule's vibrations 13,30,35,43,50,52,54,55,58,60,61,[63][64][65][66][67][68][69][70][71] .…”

Vibrationally resolved photoelectron angular distributions from randomly oriented and fixed-in-space N2and CO molecules

“…This makes calculations significantly more expensive, hence applications are scarcer, as the electronic structure must be determined for many molecular geometries, including the equilibrium one used in the fixed-nuclei approximation. For the same reason, there exist few theoretical works that have provided vibrationally resolved (or ion-energy resolved) electron angular distributions, either for randomly oriented [10,13,18,[24][25][26][27][28][29] or fixed-in-space N 2 and CO molecules. Furthermore, most of them have focused on the low-energy region.…”