Deep core photoionization of iodine in CH3I and CF3I molecules: how deep down does the chemical shift reach?

Nacer Boudjemia,Marc Simon,Kiyonobu Nagaya,Marko Huttula,Tatsuo Gejo,Kenji Tamasaku,Masaki Oura,Kari Jänkälä,Maria Novella Piancastelli

doi:10.1039/c8cp07307d

Abstract

Hard X-ray electron spectroscopic study of iodine 1s and 2s photoionization of iodomethane (CH3I) and trifluoroiodomethane (CF3I) molecules is presented. The experiment was carried out at the SPring-8 synchrotron radiation facility in Japan. The results are analyzed with the aid of relativistic molecular and atomic calculations. It is shown that charge redistribution within the molecule is experimentally observable even for very deep levels and is a function of the number of electron vacancies. We also show that the analysis of Auger spectra subsequent to hard X-ray photoionization can be used to provide insight into charge distribution in molecules and highlight the necessity of quantum electrodynamics corrections in the prediction of core shell binding energies in molecules that contain heavy atoms.

Highlights

LCPMR, F-75005, Paris, France f Department of Physics, and Astronomy, Uppsala University, SE-75120 Uppsala, Sweden has shown the feasibility of this kind of experiment, but has shed light on the novel information that can be extracted
The main aim of the present work is to investigate whether the molecular environment plays a role in such deep ionization processes, and to assess whether widespread concepts such as electronegativity and charge distribution inside a molecule extend down to very deep levels, or should the levels be considered purely atomic in nature
We begin the discussion from the iodine 2s photoelectron spectrum of CH3I and CF3I molecules, shown in panels (a) and (b) of Fig. 1

Summary

Introduction

A core-hole lifetime in the attosecond range was derived, together with direct evidence of the relative weight of radiative (photon emission) versus nonradiative (Auger) decay following K-edge ionization of Xe.[6] Following that first groundbreaking work, here we extend this research field to small polyatomic molecules, namely 1s core ionization of iodine in two representative systems, iodomethane (CH3I) and trifluoroiodomethane (CF3I). Photoelectron spectra of the 1s and 2s core levels of both molecules have been measured, and compared with Dirac–Fock theoretical calculations. Core-hole lifetimes have been extracted, and compared with previously reported values based on fluorescence measurements. As in the previous work on Kr5 and Xe,[6] the comparison of the LMX decay above and below the K-edge is informative about the importance of radiative versus nonradiative decay

Objectives

Results

Conclusion