Experimental detection and theoretical characterization of the H2–NH(X) van der Waals complex

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In this paper, we present the first correlated ab initio investigations on the ground electronic state of the O(2)-HF complex. Calculations were performed using the CCSD(T) method with the aug-cc-pVDZ and aug-cc-pVTZ basis sets. The results show that there are two equivalent minimum energy hydrogen-bonded structures of planar bent geometry, where the minima correspond to exchange of the oxygen atoms. For each minimum the length of the O-H hydrogen bond is 2.16 A. The best calculated value of D(e) of the equivalent minima is 271 cm(-1). The T-shaped geometry of the complex, with oxygen perpendicular to the axis connecting the center of masses of O(2) and the HF molecule, represents a barrier to tunneling between the equivalent minima. The best estimated value of that barrier height is 217 cm(-1). The linear O-O-HF geometry of the complex represents a saddle point. The calculated geometrical parameters of the minimum energy structure of the complex are in reasonable agreement with the previously reported spectroscopic results. However, results of the current calculations suggest that a full understanding of the fine structures of the observed infrared spectrum of the complex requires the development of an effective Hamiltonian that takes the effects of tunneling into account.

“…III A and III B. As is expected 26 and shown in Fig. 4, the BSSE corrections reduce the binding energy by almost a factor of 2 and reduce the van der Waals bond length by about 5%.…”

Section: One-dimensional Radial Potential Energy Curvessupporting

confidence: 57%

Correlated ab initio study of the ground electronic state of the O2–HF complex

Fawzy

2006

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“…Indeed, the van der Waals interactions of NH with rare gases [1][2][3][4] and small molecules [5][6][7] have been the object of detailed and careful theoretical and experimental studies over the past decades. Systematic investigations of the complexes of NH with Ar, He, and Ne or with small molecules such as NH or N 2 have yielded considerable information on structure and internal dynamics of van der Waals complexes.…”

Section: Introductionmentioning

confidence: 99%

Collisional excitation of NH(X3Σ−) by Ne: Potential energy surface, scattering calculations, and comparison with experiments

Bouhafs

Lique

2015

We present a new three-dimensional potential energy surface (PES) for the NH(X(3)Σ(-))-Ne van der Waals system, which explicitly takes into account the NH vibrational motion. Ab initio calculations of the NH-Ne PES were carried out using the open-shell single- and double-excitation coupled cluster approach with non-iterative perturbational treatment of triple excitations [RCCSD(T)]. The augmented correlation-consistent quadruple zeta (aug-cc-pVQZ) basis set was employed. Mid-bond functions were also included in order to improve the accuracy in the van der Waals well. Using this new PES, we have studied the collisional excitation of NH(X(3)Σ(-)) by Ne. Close-coupling calculations of the collisional excitation cross sections of the fine-structure levels of NH by Ne are performed for energies up to 3000 cm(-1), which yield, after thermal average, rate coefficients up to 350 K. The propensity rules between fine-structure levels are reported, and it is found that F-conserving cross sections are larger than F-changing cross sections even if the propensity rules are not as strong as for the NH-He system. The calculated rate coefficients are compared with available experimental measurements at room temperature and a fairly good agreement is found between experimental and theoretical data, confirming the good quality of the scattering calculations and also the accuracy of the potential energy surface used in this work.

“…8, is summarized in Table III, which includes the structural parameters obtained in similar calculations for the NH 3 and H 2 moieties. The calculated N¯H separation for the axial complex, 2.89 Å, compares closely with that recently calculated by Fawzy et al 16 for the HH¯NH complex, 2.85 Å. None of the distances between pairs of atoms in the NH 3 moiety was calculated to change by more than 0.001 Å from the corresponding distance for bonded and unbonded atom pairs obtained for uncomplexed NH 3 .…”

Section: Properties Of Binary Complexes Of Nh 3 With Hmentioning

confidence: 89%

“…Early experimental investigations of the complexation of H 2 by amorphous ice spurred a series of ab initio calculations, 11 16 reported a fluorescence excitation spectrum for the A 3 ⌸ − X 3 ⌺ − transition of the H 2¯N H complex. Their calculations predicted a binding energy of approximately 1.4 kJ/ mol ͑116 cm −1 ͒, as well as a secondary minimum for a T-shaped structure analogous to that of H 2¯H F. They suggested that the primary minimum is contributed by the complex with H 2 ͑j =1͒ and the secondary minimum by that with H 2 ͑j =0͒.…”

Section: Introductionmentioning

confidence: 99%

Infrared absorptions of NH3(H2) complexes trapped in solid neon

Jacox

Thompson

2006

When a very small concentration of H2 is added to a Ne:NH3=800:1 sample and the resulting mixture is deposited at 4.3 K, a new absorption appears at 4151.1 cm(-1) which can be assigned to the H2 stretching fundamental of H2 (j=1) complexed with NH3. Other new absorptions which appear near the vibrational fundamentals of NH3 are assigned to the NH3 moiety in this complex and in the complex of NH3 with H2 (j=0). The results of experiments in which HD or D2 is added to the Ne:NH3 mixture support these assignments. Ab initio and density functional calculations predict the observed infrared activation of the H2-stretching vibration for a structure in which the axis of the H2 molecule is collinear with the threefold axis of the NH3. The dependence of the observed absorption patterns on the concentration of H2 in the sample indicates that complexes of NH3 with two or more H2 molecules also form readily.