Double Core Hole Spectroscopy

Titre inermédiaire : Double inner shell vacancies of atoms and molecules
Axe Coeur de Chimie - Instrumentation

Projet de recherche mené depuis le 01/09/15. Thèse cofinancé avec le

Laboratoires porteurs
Mots clés

Double core holes, Rydberg state, direct channel, conjugate channel

Intro

This Ph.D position is co-shared between Sorbonne Universite and the University of Gothenburg. The fund for the position has been received from LabEx MiChem, which contributes the amount for the 50% of the thesis and from Knut and Alice Wallenberg foundation and the Swedish research council, which contribute the rest of the amount. According to the Swedish regulations, the duration of doctoral studies should not be less than four years, and for that reason the duration of the thesis will be extended by one year compared to the three years duration according to the French regulations. The defence of the thesis has been scheduled for July 2019.

Progress report
Figure 1: Formation of a DCH state as a result of the ejection of both core-electrons to the continuum (left) and through a core-ionization core-excitation mechanism (right) after single photon absorption.
Figure 1: Formation of a DCH state as a result of the ejection of both core-electrons to the
continuum (left) and through a core-ionization core-excitation mechanism (right) after single photon
absorption.

The subject of the thesis is the experimental study of double-core-hole (DCH) states in atoms and molecules. DCH are electronic states, formed after the simultaneous ionization or simultaneous ionization-excitation of two core electrons. Both processes are depicted in Fig. 1.

Their initial theoretical description, along with a discussion of the unique properties that these states posses, 1 were given by Cederbaum et al. [1]. As it was shown in this work and in later theoretical works [2, 3, 4], molecular DCH states where both vacancies have been created in the core shell of a single atom, referred as single site (ss) DCH, exhibit great orbital relaxation e ects, whilst the creation of the two core-vacancies in the shells of di erent atoms, known as two-site (ts) DCH, results in enhanced chemical shifts. The latter feature of DCH states can be used in order to improve the well known technique of electron spectroscopy for chemical analysis (ESCA), developed several years ago by Kai Siegbahn [5]. The application of ts-DCH in the study of extended molecular systems has already been demonstrated theoretically by Takahashi et al. [6].

Thought the initial theoretical description of DCH states was given more than thirty years ago, their experimental observation took place much later, due to the lack of the appropriate experimental setup at the time. The development of third-generation synchrotron radiation (SR) facilities and X-ray Free Electron Lasers (XFEL), allowed for a detailed probe of DCH states in di erent systems [7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17]. Using SR radiation, two experimental techniques are well-established for the study of DCH states, namely time-of-igth (TOF) coincidence spectroscopy using a magnetic bottle spectrometer and high-resolution single electron spectroscopy, using a hemispherical electron analyser. The latter technique has been used to obtain the experimental data for the purposes of this thesis. The main part of the experimental work has been conducted in the GALAXIES beamline of the French national synchrotron radiation facility SOLEIL [18, 19], Saint-Aubin, France.
The observation and identi cation of the formation of DCH states in HCl, of the type 1s-12p-12(1,3P)?*,nl as well as 1s-12s-1(1,3S)?*,ns and of double shake-up states of the general form1s-12p-1V-1 nl?n'l'?', has been achieved by our group [16]. The recorded photoelectron spectrum was interpreted by the aid of ab initio quantum chemical calculations, performed by the author, and by using a t model allowing to disentangle overlapping Rydberg states within the differentspin-orbit terms, and obtain the lifetime broadening of these core-ionized core-excited states.


Furthermore, by applying the Rydberg formula, the four di erent DIP for each spin-orbit term and the quantum defects for the ns and np Rydberg electrons were estimated. An overview of the spectrum can be seen in Fig. 2. Moreover, photoelectron spectra reecting the formation of N and C 1s-2V DCH states in CH3CN molecule, with V referring to an unoccupied valence orbital, have been recorded from us [17] and a paper is ready for submission. The spectra have been simulated by ab initio quantum chemical calculations, according to the theoretical model described in Refs [14, 15], which takes into account the direct and conjugate nature of each transition. Generally an interference of direct and conjugate channel was found for most of the observed transitions.

Within the framework of the thesis two collaborations, being of great importance, have beendeveloped. The rst is with Dr. Ralph Puttner from Freie Universitat, Berlin, Germany, whose input in the analysis of the acquired data and the discussion of the results has been indispensable for the progress of the thesis. The second is with Professor Stephane Carniato from Sorbonne Universite (LCPMR), whose theoretical support and high-level numerical simulations have allowed for a detailed interpretation of our measurements' outputs.

Beyond, the works mentioned above [16, 17], the following experimental data have been obtained
and are currently analysed:

  • Photoelectron spectra showing the formation of ss-DCH states, involving the 1s orbitals of O and S atoms in OCS molecule.
  • Photoelectron spectra of the ss-DCH and ts-DCH states of N2 and CO molecules.
  • The hyper-satellite Auger spectrum, resulting from the de-excitation of the 1s-2V and 1s-2DCH states of Argon. In order to receive theoretical support for the interpretation of the acquired data, a collaboration with a theoretical group from China has already been started on this subject.
  • A proposal submitted to the PLEIADES beam-line of SOLEIL Synchrotron, has been allocated 15 beam-time shifts, in order to study the hitherto unknown vibrational structure of DCH states, as well as other interesting phenomena, e.g. post-collision interaction (PCI), using the BF3 molecule as sample. The author will be the principal investigator (PI) of the beam-time.
Publications
  • D. Koulentianos, R. Puttner, G. Goldsztejn, T. Marchenko, O. Travnikova, L. Journel ,R.Guillemin, D. Ceolin, M.N. Piancastelli, M. Simon & R. Feifel, Phys. Chem. Chem. Phys. 20, 2724 (2018)
  • R. Feifel, J.H.D. Eland, S. Carniato, P. Selles, R. Puttner, D. Koulentianos, T. Marchenko, L. Journel, R. Guillemin, G. Goldsztejn, O. Travnikova, I. Ismail, B. Cunha de Miranda, A.F. Lago, D. Ceolin, P. Lablanquie, F. Penet, M.N. Piancastelli & M. Simon, Scienti c Reports 7, 13317 (2017) 3
  • A. Hult Roos, J.H.D. Eland, D. Koulentianos, R.J. Squibb, L. Karlsson & R. Feifel, Chemical Physics 491, 42 (2017) J. Andersson, R. Beerwerth, A. Hult Roos, R.J. Squibb, R. Singh, S. Zagorodskikh, O. Talaee, D. Koulentianos, J.H.D. Eland, S. Fritzsche & R. Feifel, Phys. Rev. A 96, 012505 (2017)
Workshops and conferences
  • Annual presentations of Ph.D students, Department of Physics, University of Gothenburg, Sweden, May 2016
  • Annual presentations of Ph.D students, Department of Physics, University of Gothenburg, Sweden, March 2017
  • Journee MiChem 2017: Les rencontres annuelles du LabEx: bilan et perspectives, Campus de Jussieu, Paris, France, June 2017
  • The international Conference on Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces, 21-24 August 2018, Budapest, Hungary: A presentation of a poster has been scheduled
References

[1] L.S. Cederbaum, F. Tarantelli, A. Sgamelloti, and J. Schirmer, J. Chem. Phys. 85, 6513 (1986)
[2] R. Santra, N.V. Kryzhevoi and L.S. Cederbaum, Phys. Rev. Lett. 103, 013002 (2009)
[3] M. Tashiro, M. Ehara and K. Ueda, Chem. Phys. Lett. 496, 217 (2010)
[4] M. Tashiro et al., J. Chem. Phys. 132, 184302 (2010)
[5] ESCA Applied to Free Molecules, edited by K. Siegbahn (North-Holland, Amsterdam, 1970)
[6] O. Takahashi et al., J. Phys. Chem. A 115, 12070 (2011)
[7] J.H.D. Eland et al., Phys. Rev. Lett. 105, 213005 (2010)
[8] P. Lablanquie et al.,Phys. Rev. Lett. 106, 063003 (2011)
[9] R. Puttner et al., Phys. Rev. Lett. 114, 093001 (2015)
[10] G. Goldsztejn et al., Phys. Rev. Lett. 117, 133001 (2016)
[11] R. Feifel et al., Scienti c Reports 7, 13317 (2017)
[12] N. Berrah et al., PNAS 108, 16912 (2011)
[13] P. Salen et al. Phys. Rev. Lett. 108, 199903 (2012)
[14] S. Carniato et al. J. Chem. Phys. 142, 014307 (2015)
[15] S. Carniato et al. J. Chem. Phys. 142, 014308 (2015)
4
[16] D. Koulentianos et al., Phys. Chem. Chem. Phys. 20, 2724 (2018)
[17] D. Koulentianos et al., to be submitted.
[18] J.-P. Rue et al. J. Synchrotron Radiat. 22, 175 (2015)
[19] D. Ceolin et al. J. Electron. Spectrosc. Relat. Phenom. 190, 188 (2013)