X-POLARIZED AND Y-POLARIZED SPECTRA OF CHLOROPHYLL-A AND PHEOPHYTIN-A IN THE RED REGION - RESOLUTION ENHANCEMENT AND GAUSSIAN DECONVOLUTION

Journal article, 1992

The red region of the X- and Y-polarized spectra obtained from the measurement of linear dichroism of chlorophyll a and pheophytin a oriented in a liquid crystal1 has been reexamined. A combination of resolution enhancement of the spectra involving their Fourier transformation and manipulation in the Fourier domain, and deconvolution into Gaussian bands on the wavenumber scale has produced results conforming to previous conclusions that place the origin of the Q(X) transition in chlorophyll a some 800-900 cm-1 to the blue relative to the origin of the Q(Y) transition. In pheophytin a, however, the separation between the Q(X) and Q(Y) bands is much larger, about 3600 cm-1. The results also confirm previous reports of an angle near 70-degrees between the transition moment directions of the Q(Y) transitions and the molecular X-axis for both chlorophyll a and pheophytin a. The resolved vibronic bands in the case of the Q(Y) transition of chlorophyll a, at least, have their counterparts in both solution spectra and high-resolution low-temperature fluorescence excitation spectra.