Single and multiple excitations in double-core-hole states of free water molecules

Abstract

We present a combined experimental and theoretical study of the double-core-hole photoelectron spectrum obtained in isolated water molecules irradiated with hard x-rays above the oxygen K −2 threshold. States of the type O K −2 V and multiply excited states are created by single-photon absorption and subsequent one-electron emission. A detailed analysis enabled by high experimental resolution reveals dissociative nuclear dynamics in the K −2 V pre-edge states. At the binding energies above the K −2 double-ionization potential, a complex spectral pattern is observed and attributed to highly excited states involving multiple shake-up excitation processes with the aid of state-of-the-art theoretical calculations. A strong broadening due to the nuclear motion indicates a highly dissociative nature of these multiply excited states, in agreement with the theoretical analysis.

The O K−2V spectrum of CO: the influence of the second core-hole

“…Finally, a high-resolution electron spectrum, recording the K À2 V states of water can be found in ref. 17. More recently, it was demonstrated from Mazza and coworkers, 28 for the case of Ne, how such K À2 V resonances can be reached using instead of SR the light produced at an XFEL.…”

“…A theoretical description of the former type of DCH states was initially given by Cederbaum et al, 23 while the first experimental fingerprints of such states were identified in the work of Ågren et al, 24 in the late seventies. Nevertheless, it was the development of third generation synchrotron radiation (SR) facilities [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] on one hand, and X-ray free electron lasers (XFEL) [18][19][20][21][22] on the other, which made the experimental observation of such states more easily accessible.…”

Hard x-ray photoelectron spectroscopy: a snapshot of the state-of-the-art in 2020

“…[341] Over the past few years, this technique has been successfully applied to a number of different atoms and molecules. [342][343][344][345][346] Another interest of DCH states is related to their highly dissociative character. Ultrafast dissociation (i.e.…”

Multi-reference approach to the computation of double core-hole spectra

“…With the advent of the newest generation of x-ray sources, double core-shell photoionization spectroscopy has been reported with unprecedented resolution either from two-photon photoelectron spectroscopy using x-ray free electron laser (X-FEL) radiation [1][2][3][4][5][6] or with single x-ray photon at synchrotron facilities. [7][8][9][10][11][12][13][14][15][16] Single-site double core hole (ssDCH or K −2 ) spectroscopy has gained special attention due to, among others, its chemical specificity and enhanced sensitivity to chemical environment when compared to single core hole (SCH) spectroscopy. 2 The higher sensitivity of ssDCH spectroscopy to the chemical environment has been demonstrated, for example, in the K −2 spectra of the C 2 H 2n (n=1-3) series, where the shift in binding energy of the first peak of C 2 H 4 relative to C 2 H 2 was measured to be ∆E C 2 H 4 /C 2 H 2 = −2.1 eV, 17 versus the value ∆E C 2 H 4 /C 2 H 2 = −0.5 eV obtained from the SCH spectra.…”