Coherent control of energy transfer in condensed phases by femtosecond phase-locked pulse pair

第一个飞秒激光脉冲在连接的蒽二聚体dithia-1,5[3,3]-蒽二聚体（DTA）中产生的分子内电子激发相干性受到第二个飞秒激光脉冲的干扰而增强或减弱，第二个飞秒激光脉冲锁相于第一个脉冲。DTA中的两个蒽环是平行堆叠的，但取向几乎是正交的。在光相位角固定为0°（同相）或180°（反相）的情况下，测量了DTA荧光干涉强度作为两个脉冲之间延迟调谐的函数。在亚皮秒区域出现了增强和衰减振荡的两个组成部分，作为延迟驯服的函数，其周期取决于激发波长。在理论分析的基础上，将这两个分量分别赋值为分子本征态的能量分裂与激光频率相对于分子电子跃迁能的失谐之间的和频和差频。导出了局部激发两个叠加态之间的激子分裂为2Δ=35cm^<-1>，这与我们之前通过荧光各向异性衰减测量得到的29cm^<-1>的结果非常吻合。

The intramolecular electronic excitation coherence created by the first femtosecond laser pulse in a linked anthracene dimer, dithia-1,5[3,3]-anthracenophane (DTA), was enhanced or depreciated by the interference with the second femtosecond laser pulse, which is phase-locked to the first pulse. Two anthracene rings in DTA are stacked parallel but with nearly orthogonal orientation. The interference intensity of fluorescence from DTA was measured as a function of delay tune between two pulses with the optical phase angle being fixed with 0° (in-phase) or 180° (anti-phase). Two components of enhanced and depreciated oscillations appeared in the sub-picoseconds region as a function of the delay tame, with the time periods depending on the excitation wavelength. On the basis of theoretical analysis, the two components were assigned to the sum and difference frequencies between the energy splitting of molecular eigenstates and the detuning of the laser frequency relative to the molecular electronic transition energy. The exciton splitting between the two superposition states of the local excitation was derived to be 2Δ=35cm^<-1>, which is in close agreement with our previous result (29cm^<-1>) obtained from fluorescence anisotropy decay measurement.