Femtosecond Dynamics and Photochemistry in Solution

Research output: ThesisDoctoral Thesis (compilation)

Abstract

The reaction dynamics of several polyatomic systems have been investigated in solution by femtosecond spectroscopy. Tetranitromethane-naphtalene complexes excited in the charge-transfer band at 400 nm undergo dissociative electron transfer, resulting in three primary products: [naphthalene].+, NO2 and C(NO2)3-. It was shown that this triad is formed within 200 fs. The subsequent competing reactions of naphthalene were followed. After ~1 ns, the main product in dichloromethane is the trinitromethylnaphtalenyl radical. In acetonitrile, the [naphthalene].+, preferentially reacts with ground state naphthalene to a dimer cation. The kinetics were reproduced by a model in which the ion pair separation rate was the primary solvent dependent parameter. Excitation of ICH2CH2I, ICF2CF2I and ICF2CF2Br at 266 nm produces haloethyl radicals and iodine atoms within 200 fs. In both fs-ps and ns-ƒÝs experiments, evidence for decomposition of these radicals were found. I2 formation within a few ps was observed from ICF2CF2I in different solvents, most likely by secondary dissociation of the radicals followed by geminate combination of iodine atoms. The predissociation rates of halobenzenes were determined in the gas phase and that of bromobenzene also in solution. Ab initio calculations on bromobenzene showed that the state reached upon excitation at 266 nm is (ƒà,ƒà*), which interacts with a repulsive triplet state. The predissociation of bromobenzene takes 28 ps in the gas phase and 9 ps in acetonitrile. The thesis also includes a study of isomerization of CH2ICl in acetonitrile and discussion of the use of two-photon absorption in neat solvents for determining pump-probe cross-correlation functions.

Details

Authors
  • Marcus Rasmusson
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Atom and Molecular Physics and Optics

Keywords

  • Kemi, Chemistry, cross-correlation function, chloroiodomethane, dihalides, bromobenzene, ion pairs, solvation, vibrational relaxation, charge-transfer, tetranitromethane, electron transfer, femtosecond spectroscopy, dissociation, Photochemistry, Fotokemi, Chemical technology and engineering, Kemiteknik och kemisk teknologi
Original languageEnglish
QualificationDoctor
Awarding Institution
Supervisors/Assistant supervisor
  • [unknown], [unknown], Supervisor, External person
Award date2001 Feb 9
Publisher
  • Villy Sundström, Department of Chemical Physics, Lund University, Box 124, 221 00 Lund, Sweden,
Print ISBNs91-7874-111-4
Publication statusPublished - 2001
Publication categoryResearch

Bibliographic note

Defence details Date: 2001-02-09 Time: 10:15 Place: Lecture Hall B, the Center for Chemistry and Chemical Engineering External reviewer(s) Name: Keiding, Sören Rud Title: Professor Affiliation: Aarhus, Denmark --- Article: I. Ultrafast formation and dissociation of trinitromethanide (C(NO2)3-) by photoinduced dissociative electron transfer and subsequent ion pair coupling reaction in acetonitrile and dichloromethane Article: Marcus Rasmusson, Eva Åkesson, Lennart Eberson and Villy Sundström Article: Accepted for publication in J. Phys. Chem. A in Jan. 2001 Article: II. Photodissociation of ICH2CH2I, ICF2CF2I and ICF2CF2Br in solution Article: Marcus Rasmusson, Alexander N. Tarnovsky, Torbjörn Pascher, Villy Sundström and Eva Åkesson Article: Will be submitted to J. Phys. Chem. A Article: III. Photodissociation of aryl halides in the gas phase studied with femtosecond pump-probe spectroscopy Article: Malin Kadi, Alexander N. Tarnovsky, Marcus Rasmusson, Jan Davidsson and Eva Åkesson Article: Will be submitted to Chem. Phys. Article: IV. Photodissociation of bromobenzene in solution Article: Marcus Rasmusson, Roland Lindh, Oliver Kühn, Malin Kadi, Villy Sundström and Eva Åkesson Article: Will be submitted to Chem. Phys. Lett. Article: V. Photodissociation dynamics of chloroiodomethane in acetonitrile studied by ultrafast pump-probe spectroscopy Article: Alexander N. Tarnovsky, Magnus Wall, Marcus Rasmusson, Torbjörn Pascher and Eva Åkesson Article: J. Chin. Chem. Soc. 2000, 47, 769-772 Article: VI. On the use of two-photon absorption for determination of femtosecond pump-probe cross-correlation functions Article: Marcus Rasmusson, Alexander N. Tarnovsky, E. Åkesson and Villy Sundström Article: Submitted to Chem. Phys. Lett. The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Chemical Physics (S) (011001060)