Characterization of the electronic ground state of Mg$_2^+$ by PFI-ZEKE photoelectron spectroscopy

TL;DR

This study uses PFI-ZEKE photoelectron spectroscopy to precisely characterize the electronic ground state of Mg$_2^+$, providing accurate energy levels, rotational constants, and improved ionization and dissociation energies.

Contribution

It presents the first detailed rotationally resolved spectra of Mg$_2^+$ ground state, yielding highly accurate spectroscopic constants and energy values.

Findings

Accurate term values and rotational constants for Mg$_2^+$ vibrational levels.

Improved measurements of ionization energy and dissociation energy.

Rotational resolution achieved in photoelectron spectra.

Abstract

The $\mathrm{X}^+\ ^2\Sigma_u^+$ ground electronic state of the Mg$_2^+$ ion has been studied by pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy. Rotationally cold Mg$_2$ molecules produced in a laser-ablation supersonic-expansion source were ionized by resonant two-photon absorption from the $\mathrm{X}\ ^1\Sigma_g^+(v"=0)$ ground vibronic state. The photoelectron spectra of the $v^+=3-14$ vibrational levels of the $\mathrm{X}^+$ state were recorded with rotational resolution and their analysis led to the determination of accurate term values and rotational constants for these levels. Improved values of the adiabatic ionization energy of $^{24}$Mg$_2$ ($51\,503.9(4)$ cm$^{-1}$) and of the ground-state dissociation energy of $^{24}$Mg$_2^+$ ($10 572.3(6)$ cm$^{-1}$) were determined from experimental data.