Ionization of 1D and 3D oriented asymmetric top molecules by intense circularly polarized femtosecond laser pulses

TL;DR

This study combines experimental and theoretical approaches to investigate how intense circularly polarized femtosecond laser pulses ionize 3D-oriented asymmetric top molecules, revealing orbital nodal plane effects on electron emission.

Contribution

It provides the first detailed analysis of strong-field ionization in 3D-oriented asymmetric top molecules, including experimental observation and theoretical modeling of nodal plane suppression effects.

Findings

Observation of characteristic splitting in photoelectron momentum distribution.

Quantitative support for the tunneling model including nodal plane effects.

Insights into electron emission suppression in molecular orbital nodal planes.

Abstract

We present a combined experimental and theoretical study on strong-field ionization of a three-dimensionally oriented 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 3-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.