Calculation of the differential two-photon ionization cross section of H2S

Abstract

Differential cross section of nonresonant two-photon ionization of the outer valence shell of H 2 S is computed using ab initio methods for several choices of photon polarization and experimental setup. The theoretical model employed is based on the second-order perturbation theory in the dipole and vertical transition approximations and the calculations are performed adopting a large basis set of L 2 integrable functions. The excitations to intermediate states are described in the random phase approximation, while the final states are described in the static-exchange approximation adopting for the continuum orbitals a K-matrix technique that allows a proper description of the angular distribution of the emitted electrons.

Electronic excitation cross sections of by electron impact

“…The SCF wavefunction is calculated from a standard [2s/6s4p] contracted basis set (Huzinaga 1965) augmented by one s (α = 0.0335), three p (α = 1.120, 0.271 and 0.0697) uncontracted functions on the hydrogen centres and three s (α = 0.0507, 0.0171 and 0.0057), four p (α = 0.0503, 0.0167, 0.0053 and 0.0027) and two d (α = 1.4137 and 0.3043) uncontracted functions on the sulphur centre. At the experimental equilibrium geometry (R H−S = 2.52 a 0 and θ H−S−H = 92.2 • ) (Snyder and Basch 1972), this basis set gives an SCF energy of −398.68 au which compares well with the calculated value of −398.61 au (Cacelli et al 1995) and an electric dipole moment of 0.43 au, exactly the same calculated value of Greer and Thompson (1994). The experimental dipole moment is 0.38 au (Gianturco 1991).…”

Density functional theory for molecular multiphoton ionization in the perturbative regime

“…The theoretical treatment of multiphoton (MP) ionization processes, in the framework of lowest order perturbation theory (LOPT), has been available for more than three decades for atomic systems. [1][2][3] Progress in the molecular case has been much slower, despite few pioneering studies by Cacelli et al 4,5 on hydrides. The paper of Boeglin et al 6 detailing the development and application of the density matrix method and a recent contribution by Son and Chu on the multiphoton ionization of N 2 and H 2 O by means of a grid-based time dependent density functional theory method, 7 are worth mentioning.…”

Multiphoton core ionization dynamics of polyatomic molecules

“…extensively applied to the atomic case [8][9][10]. In fact, with the exception of the simplest diatomic molecules H + 2 and H 2 , for which a rich literature exists [9,[11][12][13][14][15][16][17], the only systematic application of the LOPT methodology to chemically relevant molecules (hydrides) has been carried out by Cacelli et al [18][19][20].…”