Photochemical Hole Burning in Free-Base Porphyrin and Chlorin in n-Alkane Matrices

In inhomogeneously broadened lines, selective photochemistry with narrow band lasers leads to photochemical hole burning. We describe this phenomenon with particular reference to free-base porphyrin (H
2
P) and chlorin molecules in n-alkane matrices at low temperatures. It is shown that hole burning, which is permanent at low temperatures, can be used to study homogeneous optical dephasing processes as a function of temperature, to measure fast vibronic relaxation, and to assign complex vibronic spectra. Some of the parameters that are important to the potential use of photochemical hole burning for information storage in inhomogeneously broadened lines are measured and discussed.