Han Jiande, Heaven Michael C, Schnupf Udo, Alexander Millard H
Department of Chemistry, Emory University, Atlanta, GA 30322, USA.
J Chem Phys. 2008 Mar 14;128(10):104308. doi: 10.1063/1.2834932.
The CN-Ar van der Waals complex has been observed using the B (2)Sigma(+)-X (2)Sigma(+) and A (2)Pi-X (2)Sigma(+) electronic transitions. The spectra yield a dissociation energy of D(0")=102+/-2 cm(-1) and a zero-point rotational constant of B(0")=0.067+/-0.005 cm(-1) for CN(X)-Ar. The dissociation energy for CN(A)-Ar was found to be D(0')=125+/-2 cm(-1). Transitions to vibrationally excited levels of CN(B)-Ar dominated the B-X spectrum, indicative of substantial differences in the intermolecular potential energy surfaces (PESs) for the X and B states. Ab initio PESs were calculated for the X and B states. These were used to predict rovibrational energy levels and van der Waals bond energies (D(0")=115 and D(0')=183 cm(-1)). The results for the X state were in reasonably good agreement with the experimental data. Spectral simulations based on the ab initio potentials yielded qualitative insights concerning the B-X spectrum, but the level of agreement was not sufficient to permit vibronic assignment. Electronic predissociation was observed for both CN(A)-Ar and CN(B)-Ar. The process leading to the production of CN(A,nu=8,9) fragments from the predissociation of CN(B,nu=0)-Ar was characterized using time-resolved fluorescence and optical-optical double resonance measurements.
已利用B(2)Σ⁺-X(2)Σ⁺和A(2)Π-X(2)Σ⁺电子跃迁观测到CN-Ar范德华复合物。光谱得出CN(X)-Ar的离解能为D(0") = 102±2 cm⁻¹，零点转动常数为B(0") = 0.067±0.005 cm⁻¹。发现CN(A)-Ar的离解能为D(0') = 125±2 cm⁻¹。向CN(B)-Ar振动激发能级的跃迁主导了B-X光谱，这表明X态和B态的分子间势能面（PESs）存在显著差异。对X态和B态计算了从头算PESs。这些用于预测振转能级和范德华键能（D(0") = 115和D(0') = 183 cm⁻¹）。X态的结果与实验数据相当吻合。基于从头算势能的光谱模拟对B-X光谱给出了定性见解，但吻合程度不足以进行振转谱带归属。观测到CN(A)-Ar和CN(B)-Ar均存在电子预解离。利用时间分辨荧光和光-光双共振测量对由CN(B,ν = 0)-Ar预解离产生CN(A,ν = 8,9)碎片的过程进行了表征。
