We investigate an enhancement of the orientation of OCS molecules by irradiating them with a near IR (ω) ultrashort laser pulse for alignment followed by another ultrashort laser pulse for orientation, which is synthesized by a phase-locked coherent superposition of the near IR laser pulse and its second harmonic (2ω). On the basis of the asymmetry in the ejection direction of S³⁺ fragment ions generated by the Coulomb explosion of multiply charged OCS, we show that the extent of the orientation of OCS is significantly enhanced when the delay between the alignment pulse and the orientation pulse is a quarter or three quarters of the rotational period. The recorded enhanced orientation was interpreted well by a numerical simulation of the temporal evolution of a rotational wave packet prepared by the alignment and orientation pulses.

我们研究了OCS分子的取向增强，方法是先用近红外（ω）超短激光脉冲进行对准，然后再用另一超短激光脉冲进行取向，这是通过近红外激光脉冲的锁相干叠加合成的和它的二次谐波（2ω）。基于S ³⁺的喷射方向的不对称性由多电荷OCS的库仑爆炸产生的碎片离子表明，当对准脉冲和定向脉冲之间的延迟为旋转周期的四分之一或四分之三时，OCS的定向程度会显着增强。通过对由对准脉冲和取向脉冲准备的旋转波包的时间演变进行数值模拟，可以很好地解释所记录的增强取向。