Knowledge Bank

We have employed a Fourier Transform infrared Spectrometer to examine the T-T absorption spectrum of phenanthrene in PMMA at $15\circ K$ in the near IR and viaible $(5000 cm-1$ to $23000 cm-1)$ using CW excitation. T-T bands previously $reported1$ in the $10000-230000cm-1$ range have been confirmed. However, no bands were observed in the 5000 to $100000cm-1$ range. From our S/N measurements in this region we conservationvely estaimate a minimum detectable c of 50 $mole-1$ $cm-1$. We are presently investigating the $400-5000cm-1$ region in $N2$ matrices. This preliminary work demonstrates the feasibility of using the FT technique to observe absorption spectra of excited triplet species in the infrared and visible regions.