Ultrafast studies of photodissociation in solution: Dissociation, recombination and relaxation

Thesis/Dissertation · Mon May 01 00:00:00 EDT 1995

DOI:https://doi.org/10.2172/93982· OSTI ID:93982

King, Jason Christopher ^[1]

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1. Univ. of California, Berkeley, CA (United States)

Photodissociation of M(CO)₆ (M=Cr,Mo,W) and the formation of solvated M(CO)₅•S complex was studied in cyclohexane; rate-limiting step is vibrational energy relaxation from the new bond to the solvent. For both M=Cr and Mo, the primary relaxation occurs in 18 ps; for Cr, there is an additional vibrational relaxation (150 ps time scale) of a CO group poorly coupled to other modes. Relaxation of M=W occurs in 42 ps; several possible mechanisms for the longer cooling are discussed. Vibrational relaxation is also investigated for I₂^- and IBr^- in nonpolar and slightly polar solvents. Attempts were made to discover the mechanism for the fast energy transfer in nonpolar solvent. The longer time scale dynamics of I₃^- and IBr₂^- were also studied; both formed a metastable complex following photodissociation and 90-95% return to ground state in 100 ps, implying a barrier to recombination of 4.3 kcal/mol and a barrier to escape of ≥5.5 kcal/mol. The more complex photochemistry of M₃(CO)₁₂ (M=Fe,Ru) is also investigated, using visible and ultraviolet radiations, dissociation, geminate recombination, vibrational relaxation, and bridging structures and their reactions were studied. Attempts were made to extend ultrafast spectroscopy into the mid-infrared, but signal-to-noise was poor.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 93982
• Report Number(s): LBL--37349; ON: DE95016418
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CARBONYLS
CHROMIUM COMPLEXES
DISSOCIATION
IODINE BROMIDES
IODINE COMPLEXES
IODINE IONS
IRON COMPLEXES
LASER SPECTROSCOPY
MOLYBDENUM COMPLEXES
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
RECOMBINATION
RELAXATION
RUTHENIUM COMPLEXES
TUNGSTEN COMPLEXES
VIBRATIONAL STATES