Isotope shift in the Sulfur electron affinity: observation and theory

TL;DR

This study measures and theoretically analyzes the isotope shift in sulfur's electron affinity for isotopes 32S and 34S, revealing a potential anomalous shift and demonstrating agreement between experiment and advanced correlation models.

Contribution

It provides the first combined experimental and theoretical investigation of isotope shifts in sulfur's electron affinity, highlighting the role of correlation effects and mass polarization.

Findings

Measured isotope shift with large uncertainty, compatible with normal or anomalous shift.

Theoretical models predict a large specific mass shift causing an anomalous shift.

Experimental and theoretical residual shifts agree within uncertainties.

Abstract

The electron affinities eA(S) are measured for the two isotopes 32S and 34S (16752.9753(41) and 16752.9776(85) cm-1, respectively). The isotope shift in the electron affinity is found to be positive, eA(34S)-eA(32S) = +0.0023(70) cm-1, but the uncertainty allows for the possibility that it may be either "normal" (eA(34S) > eA(32S)) or "anomalous" (eA(34S) < eA(32S)). The isotope shift is estimated theoretically using elaborate correlation models, monitoring the electron affinity and the mass polarization term expectation value. The theoretical analysis predicts a very large specific mass shift that counterbalances the normal mass shift and produces an anomalous isotope shift, eA(34S)-eA(32S) = - 0.0053(24) cm-1. The observed and theoretical residual isotope shifts agree with each other within the estimated uncertainties.