Theoretical studies of the N2O van der Waals dimer: Ab initio potential energy surface, intermolecular vibrations and rotational transition frequencies

Abstract

Theoretical studies of the potential energy surface and bound states were performed for the N(2)O dimer. A four-dimensional intermolecular potential energy surface (PES) was constructed at the CCSD(T) level with aug-cc-pVTZ basis set supplemented with bond functions. Three co-planar local minima were found on this surface. They correspond to a nonpolar isomer with slipped-antiparallel planar structure and two equivalent polar isomers with slipped-parallel planar structures. The nonpolar isomer is energetically more stable than the polar ones by 162 cm(-1). To assign the fundamental vibrational frequencies for both isomers, more than 150 vibrational bound states were calculated based on this PES. The orientation of the nodal surface of the wave functions plays an important role in the assignment of disrotation and conrotation vibrational modes. The calculated vibrational frequencies are in good agreement with the available experimental data. We have also found a quantum tunneling effect between the two equivalent polar structures in the higher vibrational excited states. Rotational transition frequencies of the polar structure were also calculated. The accuracy of the PES is validated by the good agreement between theoretical and experimental results for the transition frequencies and spectroscopic parameters.

Nonpolar nitrous oxide dimer: Observation of combination bands of (14N2O)2 and (15N2O)2 involving the torsion and antigeared bending modes

“…7 The band center for the antigeared combination determined here is 2325.57517(7) cm −1 (Table II), and we therefore obtain an antigeared vibrational frequency of 96.0926(1) cm −1 for ( 14 N 2 O) 2 in the excited N 2 O ν 1 state. This is in very good agreement with the calculated values of 97.5 cm −1 from Dawes et al 10 and 97.2 cm −1 from Zheng et al 12 Of course the calculations are for the ground vibrational state while the experimental value is for the excited N 2 O ν 1 state, but in a sense the good agreement supports the idea that intramolecular vibrations do not significantly affect the frequency of this intermolecular mode. Similarly, the antigeared vibrational frequency for ( 15 N 2 O) 2 is 2255.6589(1) − 2160.1676(1) = 95.4913(2) cm −1 .…”

“…10) and 97.171 cm −1 . 12 The observations reported here demonstrate the successful application of a continuous wave external cavity QCL in our apparatus while retaining the advantages of the rapid-scan signal averaging technique. They also represent the determination of another intermolecular frequency for the N 2 O dimer, adding the antigeared bend to the previously observed out-ofplane torsion 7 and in-plane geared bend modes.…”

“…9 On the theoretical side, two independent investigations of the spectrum of the nitrous oxide dimer have been carried out recently by constructing four-dimensional (rigid monomers) intermolecular potential energy surfaces at the CCSD(T) level. [10][11][12] In both studies, the global minimum was found to be the nonpolar structure, with binding energies determined as −633 cm −1 by Dawes et al 10 and −628 cm −1 by Zheng et al 12 Both studies found the polar isomer to be the second a) Author to whom correspondence should be addressed. Electronic mail:…”

Mathematical Methods in Quantum Molecular Dynamics

“…With a (direct or nondirect) product basis, these ideas can be applied efficiently, regardless of the form and complexity of the potential energy surface (PES), provided that a direct product quadrature is used. [16,14,17,18,19,20,21,22,23,24,25].…”

Some new studies on intermolecular interaction of C3-Ar complex

“…The global two-dimensional intermolecular PES is constructed by executing two one-dimensional interpolations with the Lagrange polynomial formula [22]. The intermolecular potential energy was calculated using the supermolecular method at the level of single and double excitation coupled-cluster method with a noninteractive perturbation treatment of triple excitations (CCSD(T)) [23].…”