Retrieval of interatomic separations of molecules from laser-induced high-order harmonic spectra

TL;DR

This paper presents an iterative method to accurately determine molecular internuclear distances from high-order harmonic spectra generated by intense infrared laser pulses, enabling femtosecond-resolution chemical imaging.

Contribution

The authors introduce a novel iterative approach for retrieving molecular internuclear separations from high-order harmonic spectra, effective with minimal harmonic data and simple molecular alignments.

Findings

Accurate internuclear distances can be retrieved with few harmonics and alignment angles.

Isotropic harmonic data can also be used for linear molecules.

Iterative fitting of the transition dipole moment improves retrieval accuracy.

Abstract

We illustrate an iterative method for retrieving the internuclear separations of N$_2$, O$_2$ and CO$_2$ molecules using the high-order harmonics generated from these molecules by intense infrared laser pulses. We show that accurate results can be retrieved with a small set of harmonics and with one or few alignment angles of the molecules. For linear molecules the internuclear separations can also be retrieved from harmonics generated using isotropically distributed molecules. By extracting the transition dipole moment from the high-order harmonic spectra, we further demonstrated that it is preferable to retrieve the interatomic separation iteratively by fitting the extracted dipole moment. Our results show that time-resolved chemical imaging of molecules using infrared laser pulses with femtosecond temporal resolutions is possible.