Vibrational and K′a dependencies of the multidimensional tunneling dynamics in the 82.6 cm−1 intermolecular vibration of the water dimer-d4

Abstract

Using tunable far infrared laser absorption spectroscopy, 12 vibration-rotation-tunneling (VRT) subbands, consisting of approximately 230 transitions have been measured and analyzed for an 82.6 cm -1 intermolecular vibration of the water dimer-d 4 • Each of the VRT subbands originate from K; = 0 and terminate in either K~ = 0 or 1. These data provide a complete characterization of the tunneling dynamics in the vibrationally excited state as well as definitive symmetry labels for all VRT energy levels. Furthermore, an accurate value for the A' rotational constant of 122.9 GHz is found to agree well with its corresponding ground state value. All other excited state rotational constants are fitted, and discussed in terms of the corresponding ground state constants. In this vibration, the quantum tunneling motions are determined.to exhibit large dependencies with both the K~ quantum number and the vibrational coordinate, as is evidenced by the measured tunneling splittings. The generalized internal-axis-method (lAM) treatment, which has been developed to model the ground state tunneling dynamics, is considered for the qualitative description of each tunneling pathway, however, the variation of tunneling splittings with vibrational excitation indicate that the high barrier approximation does not appear to be applicable in the excited state. The data are consistent with a motion possessing a' symmetry, and the vibration is assigned as the Vs acceptor bending coordinate. This assignment is in agreement with the vibrational symmetry determined from the data, the results of high level ab initio calculations, and preliminary data assigned to the analogous vibration in D 2 0-DOH. 6600

Structure and Stability of Water Clusters (H2O)n, n = 8−20: An Ab Initio Investigation

“…The only available experimental result for (H 2 O) 9 69a seems to be in qualitative agreement with the predicted structure. The O-H stretch spectra of (H 2 O) 10 69a seem to support a butterfly structure and not a fused cage.…”

“…Some of the recent reviews on the subject can be found elsewhere. [2][3][4] The water dimer, the smallest water cluster which constitutes the fundamental step in the study of water clusters, has been studied in great detail experimentally [5][6][7][8][9][10][11] as well as theoretically. [12][13][14][15][16][17][18][19][20][21][22][23][24][25] It has been established that the most stable structure of a water dimer is of the C s symmetry and that it has a single hydrogen bond with a strength of 5.5 ( 0.7 kcal/ mol.…”

“…[12][13][14][15][16][17][18][19][20][21][22][23][24][25] It has been established that the most stable structure of a water dimer is of the C s symmetry and that it has a single hydrogen bond with a strength of 5.5 ( 0.7 kcal/ mol. [5][6][7][8][9][10][11] Vibrational spectroscopic studies 26 as well as some of the early ab initio studies 27 suggested an open-chain conformer with nearly linear hydrogen bonds as the most stable structure of a water trimer. Some of the other experimental [28][29][30] and theoretical [31][32][33][34][35][36][37][38][39] studies show a cyclic structure with C 1 symmetry, with two external hydrogen atoms on one side of the O-O-O plane and a third one on the other side of the plane, to be the most stable.…”

Water pair potential of near spectroscopic accuracy. II. Vibration–rotation–tunneling levels of the water dimer

“…Very precise information about the pair potential of water can be extracted, in principle, from the microwave and ͑far-͒infrared spectra of the water dimer [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] prepared in supersonic molecular beams. Many-body interactions in water have also been probed by molecular-beam spectroscopy: high-resolution far-infrared spectra were recorded for the water trimer, tetramer, pentamer, and hexamer, [18][19][20][21][22][23][24][25] mid-and near-infrared spectra for clusters up to the decamer.…”

Microwave rotation-tunneling spectroscopy of the water–methanol dimer: Direct structural proof for the strongest bound conformation

“…13 By far the most studied polyatomic•••polyatomic hydrogen-bonded complex, both computationally and experimentally, is the water-water dimer. 14,4,3,[15][16][17][18][19][20] The watermethanol dimer provides a heteromolecular analog to this well-studied system, not only to the IPS being developed for this complex but also to the permutation-inversion and vibration-rotation-tunneling formalisms created especially for this dimer. 21,1,22 Of course, methanol is chemically much different from water, but the dynamics of the unsubstituted position, whether it turns out to be donor or acceptor, should be largely conserved if the present IPS and formalism for the water-water dimer are correct and adaptable to other hydroxyl-hydroxyl interactions.…”