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Selective decomposition of water clusters by strong infrared fields: Rextification of the Lorentz force as a novel mechanism of bond breaking
KTH, School of Biotechnology (BIO), Theoretical Chemistry.
KTH, School of Biotechnology (BIO), Theoretical Chemistry.
KTH, School of Biotechnology (BIO), Theoretical Chemistry.ORCID iD: 0000-0002-1763-9383
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(English)Manuscript (preprint) (Other academic)
National Category
Theoretical Chemistry
URN: urn:nbn:se:kth:diva-25454OAI: diva2:358517
QC 20101022Available from: 2010-10-22 Created: 2010-10-22 Last updated: 2010-10-22Bibliographically approved
In thesis
1. Principles of Infrared - X-ray Pump-probe Spectroscopy
Open this publication in new window or tab >>Principles of Infrared - X-ray Pump-probe Spectroscopy
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The present thesis concerns theoretical studies of molecular interactions investigated by infrared and X-ray spectroscopic techniques, with emphasis on using these two techniques combined in pump-probe experiments. Four main types of studies are addressed: the use of near-edge X-ray absorption fine structure spectra (NEXAFS) to manifest through-bond and through-space interactions; the role of hydrogen bonding in the formation of X-ray photoelectron spectra as evidenced by simulations of the water dimer; the development of theory, with sample applications, for infrared X-ray pump-probe spectroscopy; and molecular dynamics simulations of light-induced fragmentation of water clusters.

Ab initio calculations indicate that NEXAFS spectra give direct information about the through-bond and through-space interactions between vacant non-conjugated π* orbitals. It is found out that the X-ray photoelectron spectrum of the water dimer differs dramatically from the monomer spectrum in that two bands are observed, separated by the chemically shifted ionization potentials of the donor and the acceptor. The hydrogen bond is responsible for the anomalously strong broadening of these two bands. The studies show that X-ray core electron ionization of the water dimer driven by an infrared field is a proper technique to prove the proton transfered state contrary to conventional X-ray photoelectron spectroscopy.

The physical aspects of the proposed new X-ray spectroscopic method - phase sensitive Infrared - X-Ray Pump-Probe Spectroscopy - are examined in detail using the wave packet technique in three applications; the NO molecule and the dynamics of proton transfer in core ionized water dimer and glyoxalmonoxime. It is found out that the phase of the infrared pump field strongly influences the trajectory of the nuclear wave packet on the ground state potential, which results in a phase dependence of the X-ray pump-probe spectra. A proper choice of the delay time of the X-ray pulse allows the direct observation of the X-ray transition in the proton transfered well of the core excited potential. It is found out that the glyoxalmonoxime molecule possesses an important feature; proton transfer accompanied by core hole hopping. Special attention is paid to the quantum control of the populations of vibrational level which is of crucial importance to shape the wave packet of desirable size.

The wave packet technique becomes computationally very expensive when the number of nuclear degrees of freedom is large. Molecular dynamics is used instead in studies of light-induced nuclear kinetics in the water hexamer cluster. We predict a novel mechanism of the mechanical action of light on atoms and molecules. This mechanism is based on the rectification of the Lorentz force, which gives a unique opportunity of direct site selective mechanical action of light on atoms and molecules inside large systems like clusters or biomolecules.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. x, 66 p.
National Category
Industrial Biotechnology
urn:nbn:se:kth:diva-4245 (URN)978-91-508-4 (ISBN)
Public defence
2006-12-20, FA32, AlbaNova, Roslagstullsbacken 21, Stockholm, 10:00
Available from: 2006-12-15 Created: 2006-12-15 Last updated: 2010-10-22Bibliographically approved

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