# NEAR-INFRARED TRIPLET-TRIPLET ABSORPTION SPECTRA OF XANTHENE, PHENAZINE, AND PHENOTHIAZINE DYES.

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 Title: NEAR-INFRARED TRIPLET-TRIPLET ABSORPTION SPECTRA OF XANTHENE, PHENAZINE, AND PHENOTHIAZINE DYES. Creators: Cross, Lee A. Issue Date: 1969 Publisher: Ohio State University Abstract: Triplet-triplet absorption spectroscopy has been extended to a number of heterocyclic compounds commonly used as dyes or stains. Measurements were made at room temperature by the method of flash illumination of the sample and covered the spectral region from 8,500 to $14,000 cm^{-1}$. Glycerol has proven to be a suitable solvent having a viscosity high enough so that the triplet relaxation time was on the order of $100$ microseconds. In this study, attention was fixed on water-soluble, 3-ring compounds whose 9 and 10 positions were occupied by one of the atom pairs: (C,N), (C,O), (N,N), (N,S) or (N,O). T-T transitions were found for some members of all of the above types of compounds in the region from $7000-12000{\AA}$ except for the phenoxazine (N,O) derivatives. The characteristic diffuseness of T-T transitions was not as pronounced as in the cases where the terminal level is to higher energies. In all cases, the T-T absorption bands observed had a bandwidth nearly equal to or less than the $S_{o}\leftarrow S_{1}$ absorption i the same molecule. Construction of a 5 pulse/second flash illumination system and employment of a slowly scanning monochromator with an electronic signal-averaging arrangement permitted the elimination of signal variations due to variations in the output of the flash lamp. A close, moderate resolution ($10{\AA}$) examination of the T-T bands of those compounds (mainly phenazinc derivatives) which proved to be particularly resistant to photo-decomposition and photo-oxidation was made. The structure of the T-T absorption bands obtained by these measurements was quite detailed, considering the molecular weight of the compounds investigated, some showing a regular progression whose spacing was $130 cm^{-1}$ on the long wavelength edge of the band. Description: Author Institution: Physics Department, Western Illinois University URI: http://hdl.handle.net/1811/15776 Other Identifiers: 1969-N-6