Picosecond Studies of Chemical Intermediates

Abstract

AGENCY P4AUITS) AN A CI S(E-S)I CL OMM11'4/ W MOOBG AFOS R/NC 3uilding 410, Bolling AFB DC AFOSR-8E-0014 203 32-6448 1SUPPLEM(M TAR NOTES 12&. OttWUUNiAVALAUIY SlAtUN INKER RTM OISTUt CO0lA.provf-d for public release;distrib..tion is unlimitel A&STRACT (Mwmn 200 wcvjSurface second harmonic generation (SSHG) has been used to study the chemical and physical properties of liquid interfaces.Information about th-E. thermodynamics of neat liquid surfaces has been found by observing the SH signal as a functioni of tfemperature.Extensive studies using monolayers at the air/water interface have been undertaken.Studies of acid]/base equilibrium and monolayer phase transitions Ihave-bben performed. The gas-liqjuid coexist(_ence region and an orientational phase trans.-ition has been observed.SHG was used to ntdvte interf ace properties of fused silica/e-lectrolytE solution.Orientational relaxation has been obsetved on ti? picosecon! time scale at the air/water interface bjy time-resolved second harmonic generation.The data suggests that the ground ando excited states of Rhodlamine 6G have different equilibrium orientational distributions.Ferntos-econd studies of electrons ir. liquids have characterized the g -mi rte recombination and solvation dynamics of electrons in polar and nonpolar liai.:ils. Photodet~ichment of electrons fromn halide ions in auueous solution has also b-en studics.Pi AbstractSurface second harmonic generation (SSHG) has been used to study the chemical and physical properties of liquid interfaces. Information about the thermodynamics of neat liquid surfaces has been found by observing the SH signal as a function of temperature. Extensive studies using monolayers at the air/water interface have been undertaken. Studies of acid/base equilibrium and monolayer phase transitions have been performed. The gas-liquid coexistance region and an orientational phase transition has been observed. SHG was used to study the interface properties of fused silica/electrolyte solutior. Orientational relaxation has been observed on the picosecond time scale at the air/water interface by time-resolved second harmonic generation. The data suggests that the ground and excited states of Rhodamine 6G have different equilibriu n orientational distributions.Femtosecond studies of electrons in liquids have characterized the geminate recombination and solvation dynamics of electrons in polar and nonpolar liquids. Photodetachment of electrons from halide ions in aqueous solution has also been studied. Picosecond studies of chemical intermediates have examined the role of restricted geometries on elementary chemical processes.