THE PAS AND RELAXATION PROCESS OF CHLOROP HYLL-A

The photoacoustic (PA) spectrum in amplitude and phase of chlorophyll a (chi a) has been used to study the energy level and relaxation proce sses(see Fig. 1). At the two main absorption bands S-1 and S-2 of chl, a, the phase angles are 6.5 degrees and 0 degrees, which indicate tha t the relaxation processes of excited states are different: the S-1 ba nd relaxation undergoes the lowest triplet state (T-0) while the S-2 b and relaxation does not, According to the relaxation processes, a mode l and corresponding rate equations have been established (see Fig, 2), The absorption spectrum of chi, a compared with the PA spectrum has a lso been reported (see Fig, 3), and the fluorescence quantum yield (Q) has been deduced from the intensity ratio of absorption and PA signal . The result Q=0.24 is obtained which is consistent with the original references, It is proved that the PA spectroscopy is a promising and c onvenient analytical technique in the energy levels and relaxation stu dies of biological substances.