Carbon monoxide relaxation time

The dynamics of fast processes such as electron and energy transfers and vibrational and electronic deexcitations can be probed by using short-pulsed lasers. The experimental developments that have made possible the direct probing of molecular dissociation steps and other ultrafast processes in real time (in the femtosecond time range) have, in a few cases, been extended to the study of surface phenomena. For instance, two-photon photoemission has been used to study the dynamics of electrons at interfaces [ ]. Vibrational relaxation times have also been measured for a number of modes such as the 0-Fl stretching m silica and the C-0 stretching in carbon monoxide adsorbed on transition metals [ ]. Pump-probe laser experiments such as these are difficult, but the field is still in its infancy, and much is expected in this direction m the near fiitiire. 

Meiler and Pfeifer (493) measured 13C and H NMR spectra of carbon monoxide, carbon dioxide, and benzene adsorbed on ZSM-5 and silicalite. The 13C signal from benzene was a superimposition of two lines corresponding to relatively mobile molecules (narrow Lorentzian line) and strongly adsorbed molecules (broad asymmetric line similar to that in polycrystalline benzene). Quantitative interpretation of the spectrum was possible via the measurement of the transverse proton relaxation times, T2, as a function of temperature and coverage. Recent work involving 13C NMR studies of sorbed species is summarized in Table XX. 

Sagnella, D. E. Straub, J. E. Jackson, T. A. Lim, M. Anfinrud, P. A., Vibrational population relaxation of carbon monoxide in the heme pocket of photolyzed carhonmonoxy myoglobin Comparison of time-resolved mid-lR absorbance experiments and molecular dynamics simulations. Proc. Natl. Acad. Sci. U. S. A. 1999, 96, 14324—14329. 

Time-resolved resonance Raman studies of the detailed course of cytochrome interaction with carbon monoxide gives an idea of relaxation and conformational changes in the vicinity of the actual reaction site/ A brief conference report lists rate constants for forward and reverse rate constants for interaction of deoxy-hemerythrin with dioxygen, nitrogen monoxide, hydrazoic acid, formamide, and fluoride/ ... 

Addition of singlet CDa (. 1), from the photolysis of CDa C 0, to the fluoro-olefins, Rp CF CFa (Rp = CF3, CFs CFa CFa, or CFs CFa CFa CFa CFa-) in the presence of carbon monoxide yields chemically activated cyclopropane, which may relax or expel difluorocarbene (see Scheme 4). At low pressures, ranging from <650 Torr for Rp = CFa down to <0.25 Torr for the more complex Rp = CsFii, the rate of cyclopropane decay is independent of pressure, but then it increases with increasing pressure. Relaxation of internal vibration energy is not instantaneous, the time required being longest when the vibrational modes available are fewest. ... 

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