Abstract

A method has been developed that enables resonance Raman spectra of photolabile species in solution to be recorded under conditions where the level of photoalteration is controlled: a low level enables reactant spectra to be recorded, whereas a high level enables the spectra of short-lived transient species to be recorded in real time using continuous-wave (CW) lasers and standard Raman detection equipment. The design includes a sealed flow system, enabling air-sensitive species to be studied under an inert atmosphere. A simple theoretical model has been developed to aid the interpretation of experimental results, and its applicability is demonstrated. Controlled photoalteration and its theory are demonstrated with 413.1-nm excitation of carbonmonoxymyoglobin (MbCO), which generates deoxymyoglobin (deoxy-Mb) on photolysis, and for which the spectra of both species are well established. The methods have also been applied to two air-sensitive, photolabile transition metal carbonyls using 514.5-nm wavelength excitation: for Cp₂Mo₂(CO)₆ (Cp = η⁵–C₅H₅), increasing levels of photoalteration result only in a decrease in the parent band intensities, relative to the solvent bands; for Cp₂Fe₂(CO)₄ , increasing levels of photoalteration result in the appearance of additional bands that are assigned to the transient species CpFe(μ–CO)₃FeCp, formed following the loss of a CO ligand.

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R. G. Alden, M. R. Ondrias, S. Courtney, E. W. Findsen, and J. M. Friedman
J. Opt. Soc. Am. B 7(8) 1579-1585 (1990)

Performance and design of an off-resonant continuous-wave Raman laser

K. S. Repasky, J. K. Brasseur, L. Meng, and J. L. Carlsten
J. Opt. Soc. Am. B 15(6) 1667-1673 (1998)

Multiplexed continuous-wave diode-laser cavity ringdown measurements of multiple species

Gerhard Totschnig, Douglas S. Baer, Jian Wang, Franz Winter, Hermann Hofbauer, and Ronald K. Hanson
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Continuous Recording of Raman Spectra Excited with the He–Ne Gas Laser

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