Studies on Molecular Structure and Dynamics by Doppler-free High-resolution Laser Spectroscopy

1.在高达6T的磁场下测量了反式乙二醛的A^1A_u(v_7=1)←X^1A_g跃迁的无多普勒双光子荧光激发光谱。结果表明，A^1^A_u态的塞曼分裂源于1^3BU态的自旋-轨道相互作用的混合，磁矩沿顶轴方向。2.测量了苯-d_6气体中S_1^1B_&lt；2u&gt；←S_0^1a_&lt；1g&gt；跃迁的低激发带的高分辨激发光谱和塞曼效应。在两个带中都没有观察到由与三重态相互作用引起的微扰。从塞曼光谱可以清楚地看出，旋转分辨的能级并不与三重态混合。从而得出结论：孤立苯的S_1态在低过剩能级下不可能发生系间混合。3.测量了无多普勒双光子激发光谱和萘的S_1^1B_&lt；1u&gt；(v_&lt；21&gt；=1)←S_0^1A_g(v=0)跃迁的塞曼效应。从塞曼光谱中发现，旋转分辨能级没有与三重态混合。结果表明，在S_1态激发到低共振态的孤立萘不会通过系间混合而发生无辐射衰变。用垂直于准直分子束的可调谐激光穿过S_1←S_0跃迁的0_0和0_0 22 cm~(-1)&gt~(-1)谱带，观测到了二苯并-对二恶英(DD)的亚多普勒高分辨激发光谱。将观测光谱模拟为a型跃迁，较好地再现了观测光谱，确定了S_1态为^1B_&lt；1u&gt；态。Dd分子的0_0^22 cm^&lt；-1&gt；谱带被指定为蝴蝶模的a_g分量的跃迁。

1.Doppler-free two-photon fluorescence excitation spectra of the A^1A_u(v_7=1)←X^1A_g transition of trans-glyoxal were measured under the magnetic field up to 6T. By analyzing the results, it is concluded that the Zeeman splitting of the A^1^A_u state is originating from the mixing of the 1^3Bu state by spin-orbit interaction and the magnetic moment is along the top axis.2.High resolution excitation spectra and the Zeeman effects for the low-lying vibrational band of the S_1^1B_<2u>←S_0^1A_<1g> transition in gaseous benzene-d_6 were measured. No perturbation originating from an interaction with a triplet state was observed in both bands. It became clear from the Zeeman spectra that rotationally resolved levels are not mixed with a triplet state. Accordingly, it was concluded that the intersystem mixing is not likely to occur at levels of low excess energy in the S_1 state of an isolated benzene.3.Doppler-free two-photon excitation spectrum and the Zeeman effect of the S_1^1B_<1u>(v_<21>=1)←S_0^1A_g(v=0) transition of naphthalene have been measured. Rotationally resolved levels were found not to be mixed with a triplet state from the Zeeman spectra. It is demonstrated that nonradiative decay of an isolated naphthalene excited to low rovibronic levels in the S_1 state does not occur through the intersystem mixing. 1884.Sub-Doppler high-resolution excitation spectra of dibenzo-p-dioxin (DD) have been observed for the 0_0^0 and 0_0^0+22 cm^<-1> bands of the S_1←S_0 transition by crossing a tunable laser beam perpendicular to a collimated molecular beam. The observed spectra were reproduced well by simulating the spectra as the a-type transition, and the S_1 state is identified to be a ^1B_<1u> state. The DD molecule has been shown t 0_0^+22 cm^<-1> band is assigned as a transition to the a_g component of butterfly mode.