Cold molecular ions via autoionization below the dissociation limit

TL;DR

This paper demonstrates a method to produce translationally and internally cold molecular ions, specifically DyO, via autoionization of bound levels above the ionization energy, exploiting molecules with dissociation energy exceeding ionization energy.

Contribution

It introduces a novel autoionization-based technique to generate cold molecular ions from neutral molecules with high dissociation energies.

Findings

Successfully produced cold DyO molecular ions.

Determined DyO bond dissociation energy to be 0.0831 eV above ionization energy.

Showed high efficiency in ion production through autoionization.

Abstract

Several diatomic transition metal oxides, rare-earth metal oxides and fluorides have the unusual property that their bond dissociation energy is larger than their ionization energy. In these molecules, bound levels above the ionization energy can be populated via strong, resonant transitions from the ground state. The only relevant decay channel of these levels is autoionization; predissociation is energetically not possible and radiative decay is many orders of magnitude slower. Starting from translationally cold neutral molecules, translationally cold molecular ions can thus be produced with very high efficiency. By populating bound levels just above the ionization energy, internally cold molecular ions, exclusively occupying the lowest rotational level, are produced. This is experimentally shown here for the dysprosium monoxide molecule, DyO, for which the lowest bond dissociation energy is determined to be 0.0831(6) eV above the ionization energy.