H2^+阿秒瞬态吸收中的量子路径干涉

Quantum Path Interference in Attosecond Transient Absorption of H2^+

阿秒瞬态吸收(Attosecond Transient Absorption,ATA)谱是一种非常有用的研究原子分子中亚飞秒时间尺度超快动力学的技术。通过数值求解含时薛定谔方程,模拟了氢分子离子(H2^+)在近红外(NIR)和深紫外(XUV)强复合激光场中的演化,对比了H2^+在核动和不动两种情形下ATA谱的异同。研究结果显示,当核不动时,所得的ATA谱与原子下的结构类似;当核动时,ATA谱呈现出丰富的周期调制的吸收线结构,而且其调制周期恰好等于NIR光周期的一半。通过分析H2^+的电离解离特性,证实了该半周期调制是源于H2^+基态和激发态的不同量子跃迁路径间的干涉。对比两种情形下的ATA谱,可以看出核运动对分子ATA谱的显著影响。

Attosecond transient absorption(ATA)spectroscopy is a very useful technique for studying the ultrafast dynamics of electrons in atoms or molecules on sub-femtosecond timescale.The time-dependent Schrödinger equation is numerically solved to simulate the evolution of hydrogen molecular ion(H2^+)in the intense near infrared(NIR)and extreme ultraviolet(XUV)composite laser field and to examine the ATA spectroscopy under the nuclei-fixed or nuclei-movable condition.The research shows that when the nuclei is fixed,the resulting ATA spectroscopy is similar to those of atoms.In contrast,when the nuclei is not fixed,the ATA spectroscopy exhibits richer periodically-modulated absorption line structures,whose modulation period is just equal to half of the NIR laser period.By analyzing the ionization-dissociation characteristics of H2^+,we clarify the origin of such half-periodic modulation as quantum interference among different quantum transition paths from ground to excited states.Comparing the ATA spectroscopy under different situations,one can easily distinguish the obvious influence of nuclear motion on molecular ATA spectroscopy.