Differentiation of the ground vibrational and global minimum structures in the Ar:HBr intermolecular complex

Abstract

A fully three-dimensional morphed potential energy surface is reported for Ar:HBr. The morphed potential was obtained from parametrized scaling and shifting transformations of an ab initio potential. The optimum parameters of the morphed potential were determined by a regularized nonlinear least-squares fit to available experimental data. The rovibrational dynamics of the complex were computed using an adiabatic separation of the H-Br intramolecular stretching mode from the intermolecular modes of the system. The ground rovibrational state of the morphed potential was found to have the hydrogen-bound structure Ar-HBr. This state was 10.99 cm Ϫ1 more stable than the corresponding state having the van der Waals structure, Ar-BrH, in agreement with experimental data. However, the global minimum of the morphed potential was found to have the van der Waals structure, Ar-BrH. This structure was 20.9 cm Ϫ1 lower in energy than the local minimum having the hydrogen-bound structure, Ar-HBr.

A ground state morphed intermolecular potential for the hydrogen bonded and van der Waals isomers in OC:HI and a prediction of an anomalous deuterium isotope effect

“…Two-dimensional slices of the determined 4D intermolecular morphed potential energy surface of OC:HI are given in the left panels of Figs. This is a characteristic that is very similar to what occurs in Ar-HBr, [14][15][16][17] Kr-HBr 64 as well as in He-CH 3 F. 65 The global minimum structure OC-IH is predicted to be 33͑4͒ cm −1 more stable than the corresponding local minimum associated with the OC-HI structure. The corresponding statistical uncertainties relative to the value of the potential at infinite separation of the monomers components are given in right panels.…”

“…[29][30][31][32] These effects can be particularly prominent when involved in noncovalent interactions where the influence of large amplitude anharmonic vibrations and the frequent existence of different low energy isomeric configurations manifest themselves in many phenomena whether in the gas or condensed phases. [14][15][16][17] However, in one respect, the OC:HI complex could have a property that can be distinguished from Ar-HBr and this occurs on deuteration. The interplay between these and condensed phase investigations can thus give important new insights into fundamental characteristics of noncovalent interactions.…”

Pressure broadening and shifting parameters for the spectral lines in the fundamental vibration–rotation bands of HBr and HI in mixtures with rare gases

“…Considerable progress was made during last decades in the studies of the anisotropic interaction potential energy surfaces for the HHal-Rg van der Waals complexes. Most of the presently developed PES for the HBr-Rg and HI-Rg heterodimers generated in supersonic molecular jets were based on matching the rotationally resolved microwave or IR spectral data [26][27][28][29][30][31][32][33][34]. Some purely ab initio PES were also reported [35,36].…”

High frequency wavelength modulation cw slit jet diode laser spectrometer for characterizing ground state intermolecular hydrogen bonded vibrations

“…Application of the frequency and phase stabilized submillimeter spectrometer permitted resolution of quadrupole substructure in this R band, and the precise determination of both ground and excited state parameters with microwave precision. The predictions based on near infrared combination differences with diode spectroscopy in this case gave fitted rovibrational parameters of m 0 is the band origin, B 0 is the rotational constant, D 0 J is the centrifugal distortion constant as 329618(4), 1236.32(4) and 12.55 (13) kHz compared with the more precise submillimeter analysis of 329611.4289(10), 1236.41336(5) and 12.462(2) kHz respectively [45]. The estimated frequency accuracy of the diode laser spectrometer is 30 MHz so the estimated accuracy of the origin 329618(30) MHz agrees with the accurate origin determined by submillimeter spectroscopy within this estimated error.…”

“…Such studies will provide additional, and very precise data for a critical evaluation of parameters generated in the current study. We also intend to determine a complete vibrationally morphed potential [45] for this dimer, so the data generated in this work will be used in such an analysis. However, we leave such modeling of the potential until additional experimental data is available for a more comprehensive study.…”