Controlling rovibrational state populations of polar molecules in inhomogeneous electric fields of the Stark deceleration: molecular dynamics and quantum chemistry simulations

TL;DR

This paper introduces a modified Stark-chirped rapid adiabatic passage technique that enhances rovibrational state control and deceleration efficiency of polar molecules like ammonia in inhomogeneous electric fields, combining quantum and classical simulations.

Contribution

It presents a novel state switching scheme using high-level quantum and classical simulations to improve Stark deceleration of polar molecules, achieving near-complete population inversion.

Findings

Enhanced population inversion between molecular states

Increased phase space acceptance in Stark deceleration

Improved deceleration efficiency over standard methods

Abstract

We propose a modified Stark-chirped rapid adiabatic passage technique for a robust rovibrational population transfer in the gas phase molecules in the presence of certain inhomogeneous electric fields. As an example application, the new state switching scheme is shown to greatly enhance the process of slowing polar ammonia molecules in the Stark decelerator. High-level quantum mechanical simulations show that a virtually complete population inversion between a selected pair of weak-field and strong-field seeking states of NH$_3$ can be achieved. Strong dc electric fields within the Stark decelerator are used as part of the rovibrational population transfer protocol. Classical-dynamics simulations for ammonia demonstrate notable improvements in the longitudinal phase space acceptance of the Stark decelerator upgraded with the state switching and an increased deceleration efficiency with respect to the standard Stark deceleration technique.