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Charge Transfer to Solvent Dynamics in Iodide Aqueous Solution Studied at Ionization Threshold
Kothe, Alexander

HaupttitelCharge Transfer to Solvent Dynamics in Iodide Aqueous Solution Studied at Ionization Threshold
TitelvarianteUntersuchungen der Dynamiken des Ladungstransfer an das Lösungsmittel in wässriger Iodidlösung bei der Ionisationsschwelle
AutorKothe, Alexander
Geburtsort: Homberg / Efze
GutachterProf. Dr. Emad Flear Aziz Bekhit
weitere GutachterProf. Dr. Wolfgang Kuch
Freie Schlagwörtercharge transfer; charge-transfer-to-solvent; CTTS; PES; Liquid spectroscopy; ultrafast dynamics; aqueous solution
DDC530 Physik
ZusammenfassungThis thesis explores the early-time electronic relaxation in sodium iodide aqueous solution exposed to a femtosecond ultra-violet laser pulse. Rather than initiating the charge transfer reaction by resonant one-photon photoexcitation of iodide, in the present time-resolved photoelectron spectroscopy study the charge-transfer-to-solvent (CTTS) states are populated via electronic excitation above the vacuum level. This is accomplished via a two-photon process using 266 nm (4.65 eV) laser pulses with a pulse duration of 60 fs. By analyzing the temporal evolution of electron yields from ionization of two transient species, assigned to CTTS and its first excited state, both their ultrafast population and relaxation dynamics were determined. For ionization a femtosecond laser probe photon of 3.55 eV photon energy is used. Comparison with resonant one-photon excitation studies shows that the highly excited initial states populated in the present wotk exhibit similar relaxation characteristics. Implications for structure and dynamical response of the solvation cage are discussed.

The measurements were conducted using a newly constructed experimental setup and time-of-flight electron spectrometer of the magnetic bottle type. The spectrometer was designed to measure the energy spectra of electrons generated from liquids excited by a strong laser field as well as by photons in the range from ultra-violet to soft X-rays. Its energy resolution ΔE/E is approximately 0.016 at kinetic energies of 100 eV. The collection efficiency of the spectrometer is determined for different kinetic energies, and the values are discussed for the magnetic-bottle configuration and the field-free arrangement.
Implementation of the recycle microjet technique offers uninterupted measurement condition over several hours, which is advantageous for time-resolved studies on diluted systems, and the possibility of recycling expensive or rare sample.
Inhaltsverzeichnis1 Introduction 1
2 Solvated electrons 4
2.1 Discovery and importance of solvated electrons . . . . . . . . . . . 4
2.2 Dynamics and precursors of solvated electrons . . . . . . . . . . . 8
2.2.1 The CTTS state of iodide . . . . . . . . . . . . . . . . . . 9
2.2.2 The electron detachment process . . . . . . . . . . . . . . 11
2.3 Photoexcitation of the solvated electron . . . . . . . . . . . . . . . 17
3 Experimental considerations 19
3.1 Photoelectron spectroscopy from liquids . . . . . . . . . . . . . . 19
3.1.1 Photoelectron spectroscopy . . . . . . . . . . . . . . . . . 19
3.1.2 Volatile liquids in vacuum . . . . . . . . . . . . . . . . . . 22
3.2 Time-resolved experiments using femtosecond laser pulses . . . . . 26
3.2.1 Femtosecond laser pulses . . . . . . . . . . . . . . . . . . . 26
3.2.2 The pump-probe method . . . . . . . . . . . . . . . . . . . 28
4 Experimental setup 31
4.1 Recovering of liquid samples . . . . . . . . . . . . . . . . . . . . . 32
4.2 The electron time-of-
ight spectrometer . . . . . . . . . . . . . . . 35
4.2.1 Design of the spectrometer . . . . . . . . . . . . . . . . . . 35
4.2.2 Characteristics of the spectrometer . . . . . . . . . . . . . 39
4.3 The laser system . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
5 Results and discussion 51
5.1 Sample preparation and measurement scheme . . . . . . . . . . . 51
5.2 One-color photoelectron spectra of NaI aqueous solution . . . . . 53
5.3 Time-resolved photoelectron spectra of NaI aqueous solution . . . 54
5.3.1 Transient photoelectron spectra . . . . . . . . . . . . . . . 54
5.3.2 Electron dynamics, kinetics, and modeling . . . . . . . . . 59
6 Outlook 68
6.1 Polarisation dependent transient photoelectron spectra . . . . . . 68
6.2 High-order harmonic generation (HHG) as a probe . . . . . . . . 70
7 Conclusions 75
Appendix 77
A Spectral widths of the pump and probe laser pulses 77
B Design of the HHG setup 78
List of Abbreviations 81
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SeitenzahlVI, 108 S.
Fachbereich/EinrichtungFB Physik
Erscheinungsjahr2015
Dokumententyp/-SammlungenDissertation
Medientyp/FormatText
SpracheEnglisch
Rechte Nutzungsbedingungen
Tag der Disputation10.04.2015
Erstellt am08.05.2015 - 08:51:07
Letzte Änderung08.05.2015 - 08:51:30
 
Statische URLhttp://edocs.fu-berlin.de/diss/receive/FUDISS_thesis_000000099263
URNurn:nbn:de:kobv:188-fudissthesis000000099263-3
Zugriffsstatistik