Structure, Anharmonic Vibrational Frequencies, and Intensities of NNHNN+

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• 作者：Qi Yu ; Joel M. Bowman ; Ryan C. Fortenberry ; John S. Mancini ; Timothy J. Lee ; T. Daniel Crawford ; William Klemperer ; Joseph S. Francisco
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：November 25, 2015
• 年：2015
• 卷：119
• 期：47
• 页码：11623-11631
• 全文大小：390K
• ISSN：1520-5215

文摘

A semiglobal potential energy surface (PES) and quartic force field (QFF) based on fitting high-level electronic structure energies are presented to describe the structures and spectroscopic properties of NNHNN⁺. The equilibrium structure of NNHNN⁺ is linear with the proton equidistant between the two nitrogen groups and thus of D_鈭?i>h symmetry. Vibrational second-order perturbation theory (VPT2) calculations based on the QFF fails to describe the proton 鈥渞attle鈥?motion, i.e., the antisymmetric proton stretch, due to the very flat nature of PES around the global minimum but performs properly for other modes with sharper potential wells. Vibrational self-consistent field/virtual state configuration interaction (VSCF/VCI) calculations using a version of MULTIMODE without angular momentum terms successfully describe this motion and predict the fundamental to be at 759 cm^鈥?. This is in good agreement with the value of 746 cm^鈥? from a fixed-node diffusion Monte Carlo calculation and the experimental Ar-tagged result of 743 cm^鈥?. Other VSCF/VCI energies are in good agreement with other experimentally reported ones. Both double-harmonic intensity and rigorous MULTIMODE intensity calculations show the proton-transfer fundamental has strong intensity.