Spectroscopy and dynamics of 9-hydroxyphenalenone and of its 5-methyl derivative in solid neon: Effect of methyl group upon vibrational relaxation.

Vibrational relaxation in large molecules in condensed phase is usually exceedingly fast. Very recently we have shown that, using pulsed laser excitation in low temperature matrices and time resolved fluorescence detection, one can observe and study vibrationally unrelaxed emission even from very large molecules. In this way, the relaxation and vibrational energy redistribution process in the S1 state can be investigated. In the present manuscript we use such techniques to examine the spectra and relaxation of the 5-methyl derivative of 9-hydroxyphenalenone (9-HPLN) in solid neon and compare them with those of the unsubstituted compound.