Watching Hydrogen Bonds Break: A Transient Absorption Study of Water

Ultrafast IR transient absorption measurements of the complete hydroxyl OD stretching mode spectrum of HOD in water, from 100 fs to tens of picoseconds, observe hydrogen bond breaking and monitor the equilibration of the hydrogen bond network in water. In addn., the vibrational lifetime, the time const. for hydrogen bond breaking, and the rate of orientational relaxation are detd. The reactant and photoproduct spectra of the hydrogen bond breaking process are identified by decompg. the transient spectra into two components, the initial spectrum assocd. with vibrational excited states (reactants) and the long-time spectrum assocd. with broken hydrogen bonds (photoproducts). By properly taking into account the perturbation of the reactant spectrum decay by the growth of the photoproduct spectrum, it is found that the vibrational relaxation (1.45 ps) and orientational relaxation (1.53 ps) are wavelength independent and, therefore, independent of the degree of hydrogen bonding. Energy deposited into water by vibrational relaxation does not immediately break a hydrogen bond by predissocn. nor produce a thermally equilibrated hydrogen bond distribution at an elevated temp. Following deposition of energy by vibrational relaxation, the hydrogen bond breaking time is 800 fs, and there is a transient period of several picoseconds during which the hydrogen bond distribution is not in thermal equil. [on SciFinder(R)]     «

Ultrafast IR transient absorption measurements of the complete hydroxyl OD stretching mode spectrum of HOD in water, from 100 fs to tens of picoseconds, observe hydrogen bond breaking and monitor the equilibration of the hydrogen bond network in water. In addn., the vibrational lifetime, the time const. for hydrogen bond breaking, and the rate of orientational relaxation are detd. The reactant and photoproduct spectra of the hydrogen bond breaking process are identified by decompg. the transient...     »

CAN 142:120937 66-2 Surface Chemistry and Colloids Department of Chemistry, Stanford University, Stanford, CA, USA. Journal 1089-5639 7732-18-5 (Water) Role: PEP (Physical, engineering or chemical process), PYP (Physical process), PROC (Process) (hydrogen bond breaking and equilibration of hydrogen bond network in water); 14940-63-7 (Water-d) Role: PEP (Physical, engineering or chemical process), PYP (Physical process), PROC (Process) (hydrogen bond breaking studied by OD stretching mode spectrum of HOD in water)     «

CAN 142:120937 66-2 Surface Chemistry and Colloids Department of Chemistry, Stanford University, Stanford, CA, USA. Journal 1089-5639 7732-18-5 (Water) Role: PEP (Physical, engineering or chemical process), PYP (Physical process), PROC (Process) (hydrogen bond breaking and equilibration of hydrogen bond network in water); 14940-63-7 (Water-d) Role: PEP (Physical, engineering or chemical process), PYP (Physical process), PROC (Process) (hydrogen bond breaking studied by OD stretching mode spectr...     »