Goroya Kusse G, Zhu Yu, Sun Ping, Duan Chuanxi
College of Physical Science and Technology, Central China Normal University, Wuhan 430079, China.
J Chem Phys. 2014 Apr 28;140(16):164311. doi: 10.1063/1.4872367.
The vibration-rotation-tunneling absorption spectra of the formic acid dimer (HCOOH)2 have been measured in the C-O stretch region at 1215-1240 cm(-1) using a rapid-scan tunable diode laser spectrometer in conjunction with a slit supersonic expansion. The ν5 fundamental band of the HCOOH monomer is identified and the perturbed band-center is 1220.83329(10) cm(-1). Three vibrational bands centered at 1219.71, 1225.35, and 1233.95 cm(-1) are assigned to the two combination bands and the ν22 fundamental band of (HCOOH)2 unambiguously. The transition frequencies of these three vibrational bands are fitted together using a standard Watson A-reduced Hamiltonian, yielding precise rotational and centrifugal distortion constants for each tunneling level in the ground and excited vibrational states. The fitting results of the vibrational band centered at 1225.35 cm(-1) are in good agreement with a previous high resolution study [M. Ortlieb and M. Havenith, J. Phys. Chem. A. 111, 7355 (2007)]. The tunneling splittings in the vibrationally excited states are -0.00304(16), -0.01023(11), and -0.00318(12) cm(-1), respectively, where the minus indicates that the upper tunneling component lies energetically below the lower tunneling component. A three-state deperturbation analysis using the Fermi coupling constants obtained from a previous vibrational analysis [F. Ito, Chem. Phys. Lett. 447, 202 (2007)] fails to get the normal order of the tunneling levels for all the three excited vibrational states simultaneously.
使用快速扫描可调谐二极管激光光谱仪结合狭缝超声速膨胀技术，在1215 - 1240 cm⁻¹的C - O伸缩区域测量了甲酸二聚体(HCOOH)₂的振动 - 转动 - 隧道吸收光谱。确定了HCOOH单体的ν₅基频带，其受扰带中心为1220.83329(10) cm⁻¹。明确将位于1219.71、1225.35和1233.95 cm⁻¹处的三个振动带分别归属为(HCOOH)₂的两个组合带和ν₂₂基频带。使用标准的沃森A简化哈密顿量对这三个振动带的跃迁频率进行联合拟合，得到了基态和激发振动态中每个隧道能级的精确转动和离心畸变常数。以1225.35 cm⁻¹为中心的振动带的拟合结果与先前的高分辨率研究[M. Ortlieb和M. Havenith，《物理化学杂志A》111，7355(2007)]吻合良好。振动激发态下的隧道分裂分别为 - 0.00304(16)、 - 0.01023(11)和 - 0.00318(12) cm⁻¹，其中负号表示较高隧道分量在能量上低于较低隧道分量。使用从先前振动分析[F. Ito，《化学物理快报》447，202(2007)]中获得的费米耦合常数进行的三态去微扰分析，未能同时得到所有三个激发振动态的隧道能级的正常顺序。
