Experimental Studies for structure and Isomerization Dynamics of Triplet Acetylene

采用汞光敏技术制备了正常乙炔和氘化乙炔的三重态，并用近红外二极管激光光谱对其进行了检测。在多普勒有限分辨率下，在7300 ~ 7500cm ^-^1范围内观测到1000条吸收谱线，并将其归属于A ^3B_2到d ^3A_2的电子跃迁。在不对称（K-）加倍中出现的两个等效质子或氘核的强度变化清楚地表明三重态乙炔的结构是顺弯的。带的起源和旋转常数与先前的低分辨率研究和最近的理论结果一致。测定的自旋和自旋相互作用常数在C_2H_2中是一致的。C_21-D和C_2D_2。为了揭示三重态和单重态之间的相互作用，还研究了三重态的动力学未来。利用二极管激光动力学光谱法结合脉冲汞光敏法测量了其在时间轴上的瞬态吸收谱。用Stern-Volmer分析法推算了无碰撞条件下的寿命。C_2H_2 ^3B_2态的自然寿命约为4x10 ^-^5秒。它与旋转态和自旋态（F_1）无关。₂F_3)。然而，C_2D_2的寿命是C_2H_2的三倍。这些结果将是理解从弯曲三重态激发态到线性单线态基态的内部转换机制的关键点。

The triplet states of normal and deuteride acetylene were generated by mercury photo-sensitized techniques and were detected by using near infrared diode laser spectroscopy. A thousand of absorption lines were observed in Doppler limited resolution in the 7300-7500 cm^-^1 and were assigned to the electronic transition from a ^3B_2 to d ^3A_2 state. The intensity alternation due to two equivalent protons or deuterons appeared in the asymmetry (K-)doubling clearly showed that the structure of the triplet acetylene is cis-bent. The band origin and rotational constants agrees well to a previous low resolution study and recent theoretical results. Spin rotation and spin-spin interaction constants determined are consistent among C_2H_2. C_21-D and C_2D_2.A kinetic future of the triplet state was also studied in order to reveal the interaction between the triplet and singlet states. The transient absorption profiles along the time axis were measured by using diode laser kinetic spectroscopy combined with a pulsed mercury photo-sensitized method. The lifetime at the collision free condition was extrapolated by Stern-Volmer analysis. The natural lifetime of a ^3B_2 state of C_2H_2 is about 4xl0^-^5 second. which is independent to the rotational states and spin states(F_1.F_2, F_3). However, the lifetime of C_2D_2 is three times longer than that of C_2H_2. These results would be a key point for understanding the internal conversion mechanism from the bent triplet excited state to the linear singlet ground state.