Probing molecular frame photoionization via laser generated high-order harmonics from aligned molecules

TL;DR

This paper demonstrates that high-order harmonics generated from aligned molecules can be used to retrieve detailed molecular frame photoelectron angular distributions, enabling ultrafast chemical imaging.

Contribution

It provides a theoretical framework linking high-order harmonic generation to molecular frame photoionization measurements, which was previously inaccessible.

Findings

High-order harmonic signals depend on molecular alignment angle.

Theoretical calculations match experimental harmonic phase and magnitude.

This approach enables ultrafast imaging of molecular dynamics.

Abstract

Present photoionization experiments cannot measure molecular frame photoelectron angular distributions (MFPAD) from the outermost valence electrons of molecules. We show that details of the MFPAD can be retrieved with high-order harmonics generated by infrared lasers from aligned molecules. Using accurately calculated photoionization transition dipole moments for fixed-in-space molecules, we show that the dependence of the magnitude and phase of the high-order harmonics on the alignment angle of the molecules observed in recent experiments can be quantitatively reproduced. This result provides the needed theoretical basis for ultrafast dynamic chemical imaging using infrared laser pulses.