Interference stabilization of autoionizing states in molecular $N_2$ studied by time- and angular-resolved photoelectron spectroscopy

TL;DR

This study investigates interference stabilization of autoionizing states in molecular nitrogen using time- and angular-resolved photoelectron spectroscopy, revealing different decay rates and the role of rotational couplings.

Contribution

It develops a formalism for interference stabilization in molecular ionization and demonstrates its effect on autoionizing resonances in N$_2$.

Findings

Two electronic contributions with distinct angular distributions and decay rates.

Interference stabilization is facilitated by rotationally-induced electronic couplings.

Theoretical calculations support the experimental observations.

Abstract

An autoionizing resonance in molecular N$_2$ is excited by an ultrashort XUV pulse and probed by a subsequent weak IR pulse, which ionizes the contributing Rydberg states. Time- and angular-resolved photoelectron spectra recorded with a velocity map imaging spectrometer reveal two electronic contributions with different angular distributions. One of them has an exponential decay rate of $20\pm5$ fs, while the other one is shorter than 10 fs. This observation is interpreted as a manifestation of interference stabilization involving the two overlapping discrete Rydberg states. A formalism of interference stabilization for molecular ionization is developed and applied to describe the autoionizing resonance. The results of calculations reveal, that the effect of the interference stabilization is facilitated by rotationally-induced couplings of electronic states with different symmetry.