Orientation-dependent ionization yields from strong-field ionization of fixed-in-space linear and asymmetric top molecules

Author： Hansen Jonas L Holmegaard Lotte Nielsen Jens H Stapelfeldt Henrik Dimitrovski Darko

Publisher： IOP Publishing

ISSN： 0953-4075

Source： Journal of Physics B: Atomic, Molecular and Optical Physics, Vol.45, Iss.1, 2012-01, pp. : 15101-15108

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Abstract

The yield of strong-field ionization, by a linearly polarized probe pulse, is studied experimentally and theoretically as a function of the relative orientation between the laser field and the molecule. Experimentally, carbonyl sulphide (OCS), benzonitrile and naphthalene molecules are aligned in one or three dimensions before being singly ionized by a 30 fs laser pulse centred at 800 nm. Theoretically, we address the behaviour of these three molecules. We consider the degree of alignment and orientation and model the angular dependence of the total ionization yield by molecular tunnelling theory accounting for the Stark shift of the energy level of the ionizing orbital. For naphthalene and benzonitrile, the orientational dependence of the ionization yield agrees well with the calculated results, in particular, we observe that ionization is maximized when the probe laser is polarized along the most polarizable axis. For OCS the observation of the maximum ionization yield when the probe is perpendicular to the internuclear axis contrasts the theoretical results.