Photon-momentum-induced molecular dynamics in photoionization of N$_2$ at $h\nu=40$ keV

TL;DR

This study examines how photon and electron momenta influence molecular dissociation in N$_2$ ionization at 40 keV, revealing significant effects on fragment dynamics and ion rotation.

Contribution

It provides the first detailed experimental analysis of photon-momentum effects on molecular dissociation using fully differential COLTRIMS data.

Findings

Photon and electron momenta significantly affect N$_2$ dissociation.

Recoil energy is partitioned roughly 30/70 between Auger electron and fragments.

Photon momentum induces additional rotation of the molecular ion.

Abstract

We investigate K-shell ionization of N$_2$ at 40 keV photon energy. Using a COLTRIMS reaction microscope we determine the vector momenta of the photoelectron, the Auger electron and both N$^+$ fragments. These fully differential data show that the dissociation process of the N$_2^{2+}$ ion is significantly modified not only by the recoil momentum of the photoelectron, but also by the photon momentum and the momentum of the emitted Auger electron. We find that the recoil energy introduced by the photon and the photoelectron momentum is partitioned with a ratio of approximately 30/70 between the Auger electron and fragment ion kinetic energies, respectively. We also observe that the photon momentum induces an additional rotation of the molecular ion.