Observation of Double Excitations in the Resonant Inelastic X-ray Scattering of Nitric Oxide.

Adam E A Fouda,Dirk Hauschild,Linsey C Seitz,Nicholas A Besley,Lothar Weinhardt,Monika Blum,Clemens Heske,Wanli Yang

doi:10.1021/acs.jpclett.0c01981

Abstract

The nitrogen K-edge resonant inelastic X-ray scattering (RIXS) map of nitric oxide (NO) has been measured and simulated to provide a detailed analysis of the observed features. High-resolution experimental RIXS maps were collected using an in situ gas flow cell and a high-transmission soft X-ray spectrometer. Accurate descriptions of the ground, excited, and core-excited states are based upon restricted active space self-consistent-field calculations using second order multiconfigurational perturbation theory. The nitrogen K-edge RIXS map of NO shows a range of features that can be assigned to intermediate states arising from 1s → π* and 1s → Rydberg excitations; additional bands are attributed to doubly excited intermediate states comprising 1s → π* and π → π* excitations. These results provide a detailed picture of RIXS for an open-shell molecule and an extensive description of the core-excited electronic structure of NO, an important molecule in many chemical and biological processes.

Highlights

Advances in synchrotron-based light sources have led to the emergence of x-ray spectroscopic techniques as powerful tools for the study of molecular structure and ultrafast molecular dynamics.[1,2,3,4,5,6] Among these techniques, resonant inelastic x-ray scattering (RIXS) is a twophoton technique, wherein the initial state of the system is excited to an intermediate core-excited state and the emission from the subsequent de-excitation is measured.[7]
The nitrogen K-edge RIXS map of nitric oxide (NO) shows a range of features that can be assigned to intermediate states arising from 1s®p* and 1s®Rydberg excitations; additional bands are attributed to doubly excited intermediate states comprising 1s®p* and p®p* excitations
These results provide a detailed picture of RIXS for an open-shell molecule and an extensive description of the core-excited electronic structure of NO, an important molecule in many chemical and biological processes

Summary

Introduction

Advances in synchrotron-based light sources have led to the emergence of x-ray spectroscopic techniques as powerful tools for the study of molecular structure and ultrafast molecular dynamics.[1,2,3,4,5,6] Among these techniques, resonant inelastic (soft) x-ray scattering (RIXS) is a twophoton technique, wherein the initial state of the system is excited to an intermediate core-excited state and the emission from the subsequent de-excitation is measured.[7]. The nitrogen K-edge RIXS map of NO shows a range of features that can be assigned to intermediate states arising from 1s®p* and 1s®Rydberg excitations; additional bands are attributed to doubly excited intermediate states comprising 1s®p* and p®p* excitations. The doubly excited states including a p®p* transition lead to 5σ emission at 397.7 and 398.0 eV, which is consistent with the weak bands observed in the experimental spectrum.

Results

Conclusion