Vibrationally and Spin-Orbit-Resolved Inner-Shell X-ray Absorption Spectroscopy of the NH<sup>+</sup> Molecular Ion: Measurements and ab Initio Calculations
Stéphane Carniato,
Jean-Marc Bizau,
Denis Cubaynes,
Eugene T. Kennedy,
Ségolène Guilbaud,
Emma Sokell,
Brendan McLaughlin,
Jean-Paul Mosnier
Affiliations
Stéphane Carniato
LCPMR, UMR 7614, Sorbonne Université Pierre et Marie Curie Campus, Université Pierre et Marie Curie, 4 Place Jussieu Barre 43-44, F-75005 Paris, France
Jean-Marc Bizau
Institut des Sciences Moléculaires d’Orsay, CNRS, Université Paris–Sud, and Université Paris-Saclay, F-91405 Orsay, France
Denis Cubaynes
Institut des Sciences Moléculaires d’Orsay, CNRS, Université Paris–Sud, and Université Paris-Saclay, F-91405 Orsay, France
Eugene T. Kennedy
School of Physical Sciences and National Centre for Plasma Science and Technology (NCPST), Dublin City University, Dublin 9, Ireland
Ségolène Guilbaud
Institut des Sciences Moléculaires d’Orsay, CNRS, Université Paris–Sud, and Université Paris-Saclay, F-91405 Orsay, France
Emma Sokell
School of Physics, University College Dublin, Belfield, Dublin 4, Ireland
Brendan McLaughlin
Centre for Theoretical Atomic and Molecular Physics (CTAMOP), School of Mathematics and Physics, Queen’s University Belfast, Belfast BT7 1NN, UK
Jean-Paul Mosnier
School of Physical Sciences and National Centre for Plasma Science and Technology (NCPST), Dublin City University, Dublin 9, Ireland
This article presents N2+ fragment yields following nitrogen K-shell photo-absorption in the NH+ molecular ion measured at the SOLEIL synchrotron radiation facility in the photon energy region 390–450 eV. The combination of the high sensitivity of the merged-beam, multi-analysis ion apparatus (MAIA) with the high spectral resolution of the PLEIADES beamline helped to resolve experimentally vibrational structures of highly excited [N1s−1H]*+ electronic states with closed or open-shell configurations. The assignment of the observed spectral features was achieved with the help of density functional theory (DFT) and post-Hartree Fock Multiconfiguration Self-Consistent-Field/Configuration Interaction (MCSCF/CI) ab-initio theoretical calculations of the N1s core-to-valence and core-to-Rydberg excitations, including vibrational dynamics. New resonances were identified compared to previous work, owing to detailed molecular modeling of the vibrational, spin-orbit coupling and metastable state effects on the spectra. The latter are evidenced by spectral contributions from the 4Σ− electronic state which lies 0.07 eV above the NH+2Π ground state.