Dissection of Rovibronic Structure by Polarization-Resolved Two-Color Resonant Four-Wave Mixing Spectroscopy

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• 作者：Daniel Murdock ; Lori A. Burns ; Patrick H. Vaccaro
• 刊名：Journal of Physical Chemistry A
• 出版年：2009
• 出版时间：November 26, 2009
• 年：2009
• 卷：113
• 期：47
• 页码：13184-13198
• 全文大小：541K
• 年卷期：v.113,no.47(November 26, 2009)
• ISSN：1520-5215

文摘

A synergistic theoretical and experimental investigation of stimulated emission pumping (SEP) as implemented in the coherent framework of two-color resonant four-wave mixing (TC-RFWM) spectroscopy is presented, with special emphasis directed toward the identification of polarization geometries that can distinguish spectral features according to their attendant changes in rotational quantum numbers. A vector-recoupling formalism built upon a perturbative treatment of matter-field interactions and a state-multipole expansion of the density operator allowed the weak-field signal intensity to be cast in terms of a TC-RFWM response tensor, R_Q^(K)(ε₄^*ε₃ε₂^*ε₁;J_g,J_e,J_h,J_f), which separates the transverse characteristics of the incident and generated electromagnetic waves (ε₄^*ε₃ε₂^*ε₁) from the angular momentum properties of the PUMP and DUMP resonances (J_g,J_e,J_h,J_f). For an isolated SEP process induced in an isotropic medium, the criteria needed to discriminate against subsets of rovibronic structure were encoded in the roots of a single tensor element, R₀⁽⁰⁾(ε₄^*ε₃ε₂^*ε₁;J_g,J_e,J_h,J_e). By assuming all optical fields to be polarized linearly and invoking the limit of high quantum numbers, specific angles of polarization for the detected signal field were found to suppress DUMP resonances selectively according to the nature of their rotational branch and the rotational branch of the meshing PUMP line. These predictions were corroborated by performing SEP measurements on the ground electronic potential energy surface of tropolone in two distinct regimes of vibrational excitation, with the near-ultraviolet ¹B₂−¹A₁ (π*←π) absorption system affording the requisite PUMP and DUMP transitions.