# Photodissociation Dynamics in (N2) n + Clusters

## TL;DR

This study investigates how nitrogen clusters break apart when exposed to UV light, revealing that N4+ is a key player in the process.

## Contribution

The paper provides new insights into the photodissociation dynamics of nitrogen clusters and the role of N4+ as a chromophore.

## Key findings

- N4+ is identified as the chromophore in larger nitrogen clusters.
- N4+ fragments from larger clusters have lower kinetic energy than N2+ fragments.
- Photodissociation and recombination processes are mediated by the surface of the clusters.

## Abstract

(N2)
n

+ cluster
ions are produced and cooled in a pulsed-discharge supersonic expansion
and studied with UV laser photodissociation and velocity-map imaging
(VMI). All cluster sizes up to n = 15 absorb strongly
near 355 nm, and those with n > 3 dissociate to
produce
both N2
+ and N4
+ photofragments.
This suggests that the N4
+ ion is the chromophore
in the larger clusters, consistent with the previous optical spectroscopy
and bond energy determinations. Photofragment imaging of N4
+ produces an anisotropic distribution peaked along the
laser polarization. Analysis of the maximum kinetic energy release
produces a dissociation energy consistent with values determined in
previous experiments. Dissociation of larger clusters produces N2
+ with significant kinetic energy values that do
not change appreciably with cluster size. This suggests that the N4
+ core ion is not enclosed by the clustering of
additional N2 molecules. N4
+ fragments
from larger clusters have somewhat lower kinetic energies than the
N2
+ fragments, consistent with recombination
or partial caging after dissociative recoil. However, the kinetic
energy release of N4
+ is also considerable and
it persists in the dissociation of larger clusters. This suggests
that the N4
+ ion in these clusters resides near
the surface and that the photodissociation and recombination are mediated
by this surface rather than by a true caging effect.