Manipulation of Rotational States With Varying Pulse Parameter: Achieving High Molecular Alignment and Orientation for CH3F

Abstract

Increasing interest in the fields of high-harmonics generation, laser-induced chemical reactions, and molecular imaging of gaseous targets demands high molecular alignment and orientation (AnO). In this work, we examine the critical role of different pulse parameters on the field-free AnO dynamics of the CH3F molecule, and identify experimentally feasible optical and THz range laser parameters that ensure maximal AnO for such molecules. Herein, apart from rotational temperature, we investigate effects of varying pulse parameters such as, pulse duration, intensity, frequency, and carrier envelop phase (CEP). By analyzing the interplay between laser pulse parameters and the resulting rotational population distributions, the origin of specific AnO dynamics was addressed. We could identify two qualitatively different AnO behaviors and revealed their connection with the pulse parameters and the population of excited rotational states. We report here the highest alignment of ⟨cos2θ⟩=0.843 andorientation of⟨cos(θ)⟩=0.886 for CH3F molecule at 2K using single pulse. Our study should be useful to understand different aspects of laser-induced unidirectional rotation in heteronuclear molecules, and in understanding routes to tune/enhance AnO in laboratory conditions for advanced applications.