Spinning a pseudorotating molecular top by means of a circularly polarized infrared laser pulse: Quantum simulations for ¹¹⁴CdH₂

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• 作者：Ingo Barth ; Jö ; rn Manz ; Peter Sebald
• 关键词：Circularly polarized laser pulse ; Linear molecule (CdH₂) ; Nuclear dynamics ; Pseudorotation ; Vibrational and pseudorotational states
• 刊名：Chemical Physics
• 出版年：2008
• 期刊代码：18_03010104
• 类别：ch
• 出版时间：4 May 2008
• 卷：346
• 期：1-3
• 页码：89-98
• 文件大小：594 K

摘要

A circularly polarized infrared (IR) laser pulse which propagates along the axis of a pre-aligned linear polyatomic molecule may excite unidirectional pseudorotations corresponding to excitation of the molecular bend and rotation of the bent molecule around that axis. This preparation and spinning a molecular top is, in part, analogous to the generation of unidirectional electron circulation in molecules by means of circularly polarized ultraviolet (UV) laser pulses [I. Barth, J. Manz, Angew. Chem. 118 (2006) 3028; Angew. Chem., Int. Ed. 45 (2006) 2962], allowing to apply similar methods for the laser driven wavepacket dynamics. It is demonstrated here by means of quantum simulations of the laser driven wavefunction Ψ(t) of the model system , where Ψ(t) is expanded in terms of vibrational eigenfunctions Ψ_vl which are labeled by quantum numbers b67e188e0ccd6afe7d9ef4facf82"> for the vibrations (v) including the symmetric stretch (s), bend (b), antisymmetric stretch (a), and for the pseudorotation (l). The corresponding vibrational and pseudorotational eigenenergies and matrix elements for the model ¹¹⁴CdH₂ are adapted as approximations from accurate values which have been determined previously, for simulations of high resolution IR spectra. These dipole matrix elements and related selection or propensity rules imply dominant ladder climbing or 0⁰→1^-1→2^-2→, i.e., sequential populations of the states with increasing quantum numbers for the bends and pseudorotations , where 17b72ff" title="Click to view the MathML source" alt="Click to view the MathML source">l=+v_b or l=-v_b depending on the right (+) or left (-) circular polarization of the IR laser pulse, respectively.