Investigation of the ground vibrational state structure of H35Cl trimer based on the resolved K, J substructure of the ν5 vibrational band

Abstract

Investigation of an H-bonded dimer: Calculations of bonding structures and temperature dependence of the librational substructure of the OH-stretching band Dipole moment analysis of excited van der Waals vibrational states of ArH35ClThe high resolution rovibrational IR spectrum of the antisymmetric H 35 CI stretching lI5 vibrational band in the (H 35 Clh isotopomer of the trimer has been measured with a tunable infrared diode laser supersonic jet spectrometer. One of the most prominent features of the spectrum is a series of strong lines each formed with P P or rR transitions, with resolved K, J substructure developing between two adjacent P P or rR heads. Analyzing the spectrum of (H 35 Clh as the perpendicUlar band of an oblate symmetric rovibrator, the following molecular parameters have been obtained: lIo-C' {;=2809.776 98 (6) cm-I, B"=6.804 14(55) X 10-2 em-I, B' =6.859 43(55) X 10-2 em-I, c' -C"=2. 737(78)X 10-4 cm-I, D~K=-8.40(38)XlO-7 cm-I , D;K=-8.14(38)XlO-7 cm-I , D;=4.26(16)XlO-7 cm-I, D;=4.16(16)XlO-7 cm-I , D~=4.32(22)XlO-7 cm-r, D~=4.16(22)XlO-7 cm-I . A relationship among the centrifugal distortion constants establishes that the geometry of (H 35 Clh is consistent with a dynamically averaged planar ground vibrational state. The centers of mass of the H 35 CI components are separated by 3.693(1) A in this structure. Ab initio methods were also used to estimate the splitting due to the tunneling motions between clockwise (cw) and counterclockwise (ccw) identical structures. Both theoretical and experimental evidence indicate that the (HClh complex has a planar eqUilibrium structure with no observable tunneling probability between the cw and ccw forms, thus the molecular symmetry group of the complex is proposed to be C 3h (M).

Study of HCl Clusters in Helium Nanodroplets: Experiments and ab Initio Calculations as Stepping Stones from Gas Phase to Bulk

“…The most intense peak in the spectrum at 2807.7 cm -1 is assigned to the cyclic trimer based on the pick-up cell pressure dependence experiments (see Figure S3 in the Supporting Information). It is also in good agreement with results of previous experiments in the gas phase, 5,9,10,32,33 which are listed in Table 1. Similarly, the strong peak at 2772.3 cm -1 is assigned to the cyclic tetramers.…”

The cyclic ground state structure of the HF trimer revealed by far infrared jet-cooled Fourier transform spectroscopy

“…The first high resolution (HR) spectra of these hydrogen bonded complexes enabled access to the dimer structure, dissociation energy, predissociation lifetimes and tunneling dynamics, and ultimately permitted us to build reliable intermolecular potential energy surfaces for such four-atom clusters. 4,49,50 In contrast to the large number of hydrogen bonded dimer studies reported up to now, only a few homomolecular trimers such as (HCCH) 3 , 51 (HCN) 3 , 52 (HF) 3 , 9,36 (HCl) 3 , 53 (CO 2 ) 3 , 54,55 (DF) 3 , 41 and (H 2 O) 3 56 have been studied in nearly isolated gas phase supersonic jet environments associated with near or far infrared (FIR) tunable laser spectroscopy. Apart from (HF) 3 , molecular constants could be obtained from rotationally resolved vibrational spectra.…”

“…The donor stretching modes recorded for (HCl) 3 and (DF) 3 have pointed out the problems related to the analysis of higher energy bands: depending on the high density of levels and the strength of the coupling with the bath of states via intramolecular vibrational redistribution (IVR) a loss of fully resolved structure due to significant lifetime homogeneous broadening is likely to be observed, which is indeed large for (DF) 3 (4 GHz) 41 but much smaller for (HCl) 3 (r90 MHz). 53 Nevertheless, spectral analysis from such experiments provided reliable information about the structure and dynamics of trimers. This is not the case of the hydrogen fluoride trimer and larger clusters for which available experimental IR data beyond cryogenic matrix spectra are very scarce.…”

“…The large values of the equilibrium (D e ) and corrected harmonic zero-point vibrational energy (D 0 ), dissociation energies, respectively calculated at 16 and 10.7 kcal mol À1 for (HF) 3 , clearly underline the presence of three intermolecular bonds to form the cyclic structure (rather than two for a chain conformation). 36,41,53,56 The character of the normal modes of (HF) n oligomers can be classified according to group theory and vibrational coordinate analysis upon a planar oblate symmetric top having a C nh structure: H-F intramolecular stretches in the 3300-3700 cm À1 range, H-F intermolecular librations in the 500-1100 cm À1 range, F-F intermolecular stretches below 350 cm À1 and ring deformations below 100 cm À1 .…”

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

“…This spectrometer involved the use of lead salt tunable diode lasers in the range of 3-5 lm and took advantage of comparable wavelength modulation to achieve a minimum detectable absorption of 3 · 10 À5 . Various molecular complexes have been investigated using this spectrometer [25][26][27][28][29][30][31][32][33], and have yielded excellent results for a range of intramolecular vibrations in molecular complexes, but usually inadequate sensitivity was available for generation of the necessary data for low frequency intermolecular rovibrational parameters for these weakly bound species. In order to overcome such limitations, we now report the development of a diode laser spectrometer that incorporates the ultrasensitive high frequency wavelength modulation static gas phase methods [34][35][36] for operation in cw supersonic jet expansions.…”