Strongly aligned gas-phase molecules at Free-Electron Lasers

TL;DR

This paper presents a new method for strongly aligning gas-phase molecules at high repetition rates using chirped laser pulses at free-electron laser facilities, enabling precise molecular orientation for x-ray experiments.

Contribution

The study introduces a novel experimental approach utilizing in-house chirped laser pulses for strong molecular alignment at free-electron laser facilities.

Findings

Achieved a degree of alignment of 0.85 in molecules.

Alignment limited by molecular beam temperature, not laser system.

Method compatible with existing short-wavelength laser systems.

Abstract

We demonstrate a novel experimental implementation to strongly align molecules at full repetition rates of free-electron lasers. We utilized the available in-house laser system at the coherent x-ray imaging beamline at the Linac Coherent Light Source. Chirped laser pulses, i. e., the direct output from the regenerative amplifier of the Ti:Sa chirped pulse amplification laser system, were used to strongly align 2,5-diiodothiophene molecules in a molecular beam. The alignment laser pulses had pulse energies of a few mJ and a pulse duration of 94 ps. A degree of alignment of $\left<\cos^2\!\theta_{2D}\right>$ = 0.85 was measured, limited by the intrinsic temperature of the molecular beam rather than by the available laser system. With the general availability of synchronized chirped-pulse-amplified near-infrared laser systems at short-wavelength laser facilities, our approach allows for the universal preparation of molecules tightly fixed in space for experiments with x-ray pulses.