Multiple photon excitation and selective reactions of hydrocarbons doped in low temperature crystals

1.低温晶体中孤立分子由于声子边带贡献的减少而具有尖锐的吸收线，因而容易被选择性激发。在低温固体中，振动弛豫预计相对较慢。本研究的目的是在低温稀有气体晶体中分离多原子小分子，并研究分离分子的物理行为.详细研究了氧分子的情况。在Ar或Kr晶体中孤立氧分子，用KrF激光照射时，新发现了由高振动激发基电子态到高电子态跃迁的吸收线，分析了吸收线的位置和时间行为，给出了高B电子态的势能曲线。对于硫化氢和某些氯氟烃，只有当它们被稀释到1/10000以下时，才有可能分离。这些分离的分子可以被KrF准分子激光照射解离，但不能被红外TEA二氧化碳激光照射。后者可能是由于在中间阶段相对较快的振动弛豫和/或红外多光子吸收过程中的能量失配。

1. The isolated molecules in low temperature crystals are expected to possess sharp absorption lines due to the decrease of the contribution of the phonon side bands, and thus selective excitation of the molecules may be easy. The vibrational relaxation is expected to be relatively slow in low temperature solids. The objective of the present research is to isolate small polyatomic molecules in low temperature rare-gas crystals and to pursue the photophysical behavior of the isolated molecules.2. The case of oxygen molecules was studied in detail. When the oxygen molecules were isolated in Ar or Kr crystals and irradiated by KrF laser light, absorption lines assigned to the transition from the highly vibrationally excited ground electronic state to a higher electronic state were newly found. Analysis of these line positions and time behaviors gave the potential curve of the upper B electronic state, and also the mechanism and rates of the very slow relaxation of the vibrational states.In the case of hydrogen sulfide and some chlorofluorohydrocarbons, the isolation was only possible when they were diluted to less than 1/10000. These isolated molecules could be dissociated by KrF excimer laser irradiation, but not by infrared TEA carbon dioxide laser irradiation. The latter may be due to the relatively fast vibrational relaxation in the intermediate stages and/or energy mismatch during the infrared multiple photon absorption.