Photoionization of CH4, H2O and NH3 within a Sturmian approach

C.M. GRANADOS{CASTRO, G. GASANEO, D.M. MITNIK, AND L.U. ANCARANI

Bordeaux

Congreso; Colloque commun de la division de Physique Atomique et Moléculaire et Optique de la SFP et des Journées de Spectroscopie Moléculaires; 2016

La Societe Francaise d'Optique

(PI) of atoms (see [1], and references therein). Their application to molecular systems is generally notstraightforward because of the appearance of several challenges, amongst which the spatial orientationof the target (not resolved experimentally), the description of the non-central Hamiltonian and the correspondingcontinuum states. Finding an accurate representation of such states is not an easy task.The Sturmian approach [2], which uses Generalized Sturmian Functions (GSF), has been appliedsuccessfully to atomic ionization processes. In this contribution, we apply its extension to molecular systems[2], in particular to PI of CH4, NH3 and H2O.Within a single active-electron approximation and theone-center expansion (OCE), we solve the time-independent, first-order perturbative, Schr¨odinger equation,expanding the scattering wave function in a GSFs basis set. Their adequate asymptotic behavior (inthis case outgoing Coulomb behavior, corresponding to a +1 charge felt at large distances by the escapingphotoelectron) allows us to extract the transition amplitudes directly from the expansion coefficients [1].The random spatial orientation of the target is included using either a post-averaged or a pre-averagedscheme. For the scattering potential, we use a molecular model potential [3] (in both versions : a centraland a noncentral). Cross section results for both schemes are compared in order to investigate whetherthe second option (which is computationally much lighter) is acceptable or not.Figure 1 provides an example, for ionization from the outer valence orbital 1b1 of H2O.