Long-Lasting Orientation of Symmetric-top Molecules Excited by Two-Color Femtosecond Pulses

TL;DR

This paper investigates a novel long-lasting, field-free molecular orientation effect in symmetric-top molecules induced by two-color femtosecond pulses, which persists beyond the pulse duration and depends on molecular interactions and experimental parameters.

Contribution

It introduces the concept of long-lasting orientation caused by combined polarizability and hyperpolarizability effects, expanding understanding of molecular control with ultrafast laser pulses.

Findings

Long-lasting orientation persists until disrupted by physical effects.

Orientation degree depends on temperature and pulse parameters.

Potential applications include molecular deflection control via harmonic generation.

Abstract

Impulsive orientation of symmetric-top molecules excited by two-color femtosecond pulses is considered. In addition to the well-known transient orientation appearing immediately after the pulse and then reemerging periodically due to quantum revivals, we report the phenomenon of field-free long-lasting orientation. Long-lasting means that the time averaged orientation remains non-zero until destroyed by other physical effects, e.g. intermolecular collisions. The effect is caused by the combined action of the field-polarizability and field-hyperpolarizability interactions. The dependence of degree of long-lasting orientation on temperature and pulse's parameters is considered. The effect can be measured by means of second (or higher-order) harmonic generation, and may be used to control the deflection of molecules traveling through inhomogeneous electrostatic fields.