凝聚相中血卟啉分子的激光选择激发

用脉冲染料激光器在77K对血卟啉在乙醇和HCl溶液中的电子振动带和0—0跃迁带进行激光选择激发,得到了有振动结构的荧光光谱,发现其对激发波长有明显的选择性。在冷凝的乙醇溶液中,HPD的荧光出现四种不同的特征,在选择激发下给出更好的分辨。认为它可能与异构现象有关。

LASER SELECTIVE EXCITATION OF HEMATOPOR-PHYRIN IN THE CONDENSED PHASE

The hematoporphyrin have several isomers. These isomers often exist in two types, alternate substitute and non-symmetry substitute.At the room temperature, the spectra of the hematoporphyrin in solution have the character of broad band, which have no vibronic structure and can not give the feature of the different isomers.Using the flashlamp pumped tunable Rh 6G dye laser, we was made the selective excitation for the electronic-vibronic levels of the hematoporphyrin in the ethanal at 77K. In experiment, the laser linewidth taken is lager than the homogeneous linewidth and narrower than the inhomogeneous linewidth, in order to distinguish the different feature of the isomer. The results show that four narrowed peaks appear in the region of 0-0 transition for different excitative wavelength. It is possible that these peaks belong to isomer molecules with the electronic vibranica transition frequency as consistent with the laser excitative freguency. Since the vibronic levels of the different molecules superposed each other,several peaks simultaneously was observed in the region of the 0-0 transition. The position of different 0-0 transition peaks are relatively shifted from difference of the structure symmetry. Two peaks appeared in the fluorescence spectra at 77K belong to two main kinds of the isomer.In (1N) HCl solution, since the structural symetry increased the fluorescent spectra occured blue-shift. Thus 0-0 transition band lies on the region of 570-600nm, which just consistent with the tunable range of the Rh 6G dye laser. The structural fluorescent spectra are occured by laser selective excitation in the region of 0-0 transition. When excitation at λ=591.3nm the vibronic structure is clear but as the excitative wavelength shortened the structure disappears stepwise. This phenomenon can. be interpret as overlaping of the pure electronic transition with the phonon sideband in the shorter wavelength side of the 0-phonon line. The experimental results indicated that the electronic-phonon coupling of the HPD in these solvent is not very strong.