Single vibronic level, or dispersed, fluorescence

From about 1970, but before the availability of suitable lasers, Parmenter and others obtained SVLF spectra, particularly of benzene, using radiation from an intense high-pressure xenon arc source (see Section 3.4.4) and passing it through a monochromator to select a narrow band ca 20 cm wide) of radiation to excite the sample within a particular absorption band. 

Dye lasers, frequency doubled if necessary, provide ideal sources for such experiments. The radiation is very intense, the line width is small ( 1 cm ) and the wavenumber may be tuned to match any absorption band in the visible or near-ultraviolet region. 

Pyrazine belongs to the D2h point group, and Table A.32 in Appendix A shows that since B u = r(Tj) the Oq band is polarized along the x axis, which is perpendicular to the molecular plane. 

Numbering is based on the Wilson numbering for the analogous vibrations of benzene. 

The value of these characteristic fragmented contours in making assignments is apparent. 

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Single vibronic level, or dispersed, fluorescence spectroscopy... 

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