Lauzin C, Didriche K, Liévin J, Herman M, Perrin A
Laboratoire de Chimie quantique et Photophysique, CP160/09 Faculté des Sciences, Université Libre de Bruxelles, Ave. Roosevelt, 50 B-1050 Brussels, Belgium.
J Chem Phys. 2009 May 28;130(20):204306. doi: 10.1063/1.3137069.
A slit nozzle supersonic expansion containing acetylene [492 SCCM (SCCM denotes cubic centimeter per minute at STP)] and carbon dioxide (740 SCCM) seeded into Ar (837 SCCM) is investigated using cw-cavity ring-down spectroscopy, in the 1.5 microm range. The C(2)H(2)-CO(2) van der Waals complex is observed around the nu(1) + nu(3) acetylenic band. The rotational temperature is estimated to be close to 60 K from the comparison between observed and simulated spectra. The analysis of the main, perturbed B-type band centered near 6,549.280 cm(-1), is performed. It is attributed to a dimer with the known planar, C(2v) geometry. The present overtone data, involving ground state levels with higher J/K states (J < or = 35 and K(a) < or = 20) than previously reported, are combined to 3 microm data [D. G. Prichard, R. N. Nandi, J. S. Muenter, and B. J. Howard, J. Chem. Phys. 89, 1245 (1988); Z. S. Huang and R. E. Miller, Chem. Phys. 132, 185 (1989)] to determine improved ground state parameters. The major perturbations affecting the upper state are accounted for through C-type Coriolis resonances involving one dark state, whose symmetry must therefore be A(1). Upper state constants are obtained for the bright and dark states. The dependence upon vibrational excitation is demonstrated to arise from excitation in the acetylene unit, only, for the former, but cannot be unravelled for the latter.
利用连续波腔衰荡光谱技术，在1.5微米范围内对一个包含乙炔[492标准立方厘米每分钟（标准立方厘米表示在标准温度和压力下每分钟的立方厘米数）]和二氧化碳（740标准立方厘米每分钟）并注入氩气（837标准立方厘米每分钟）的狭缝喷嘴超声速膨胀进行了研究。在乙炔基频带的ν(1)+ν(3)附近观测到了C₂H₂-CO₂范德瓦尔斯复合物。通过观测光谱与模拟光谱的比较，估计转动温度接近60K。对位于6549.280厘米⁻¹附近的主要受扰B型谱带进行了分析。它被归因于具有已知平面C₂v几何结构的二聚体。将目前涉及比先前报道更高J/K态（J≤35且Ka≤20）基态能级的泛音数据与3微米数据[D.G.普里查德、R.N.南迪、J.S.穆恩特和B.J.霍华德，《化学物理杂志》89，1245（1988）；Z.S.黄和R.E.米勒，《化学物理》132，185（1989）]相结合，以确定改进的基态参数。影响上能级的主要微扰通过涉及一个暗态的C型科里奥利共振来解释，因此其对称性必定为A₁。获得了明亮态和暗态的上能级常数。结果表明，对于前者，对振动激发的依赖性仅源于乙炔单元中的激发，但对于后者则无法阐明。
