Ionization of one- and three-dimensionally-oriented asymmetric-top molecules by intense circularly polarized femtosecond laser pulses

Abstract

We present a combined experimental and theoretical study on strong-field ionization of a three-dimensionallyoriented asymmetric top molecule, benzonitrile (C 7 H 5 N), by circularly polarized, nonresonant femtosecond laser pulses. Prior to the interaction with the strong field, the molecules are quantum-state selected using a deflector and three-dimensionally (3D) aligned and oriented adiabatically using an elliptically polarized laser pulse in combination with a static electric field. A characteristic splitting in the molecular frame photoelectron momentum distribution reveals the position of the nodal planes of the molecular orbitals from which ionization occurs. The experimental results are supported by a theoretical tunneling model that includes and quantifies the splitting in the momentum distribution. The focus of the present article is to understand strong-field ionization from 3D-oriented asymmetric top molecules, in particular the suppression of electron emission in nodal planes of molecular orbitals. In the preceding article [Dimitrovski et al., Phys. Rev. A 83, 023405 (2011)] the focus is to understand the strong-field ionization of one-dimensionally-oriented polar molecules, in particular asymmetries in the emission direction of the photoelectrons.

Resonance signatures in the body-frame valence photoionization of CF4

“…This can be achieved through 3-D laser alignment when feasible 6 or, in the case of dissociative ionization, reconstructed through coincident electron-ion momentum imaging techniques, such as COLTRIMS (COLd Target Recoil Ion Momentum Spectroscopy) 7 . In the latter case, the time scale for Laser alignment prior to photoionization is limited to molecules with an asymmetric polarizability and thus not applicable to a highly symmetric molecule such as CF 4 .…”

Probing the dynamics of dissociation of methane following core ionization using three-dimensional molecular-frame photoelectron angular distributions

“…To measure an MFPAD, the gas phase molecule must be oriented accurately in the lab frame. Such orientation can be accomplished prior to the ionization by laser alignment [4,5]. The orientation of the molecule at the time of photoionization can also be determined in the case of core or inner shell ionization by detecting the photoelectron in coincidence with positively charged fragments that emerge following prompt Auger decay and dissociation of the molecule [6].…”

Rotational dynamics of an asymmetric-top molecule in parallel electric and nonresonant laser fields

“…3 and α zz = 18.64Å 3 [40,41] For the sake of simplicity, we restrict this study to several rotational states of even parity with respect to the reflections on XZ-plane and under a π-rotation around the MFF z-axis. We stress that the observed physical phenomena also appear for levels within other irreducible representations.…”