Communication: Determination of the bond dissociation energy ( D ) of the water dimer, (H2O)2, by velocity map imaging

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Communication: Determination of the bond dissociation energy (D0) of the water dimer, (H2O)2, by velocity map imaging The Journal of Chemical Physics 134, 211101211101 (2011) We report the definition and testing of a new ab initio 12-dimensional potential for the water dimer with flexible monomers. Using our recent accurate CCpol-8s rigid water pair potential [W. Cencek, K. Szalewicz, C. Leforestier, R. van Harrevelt, and A. van der Avoird, Phys. Chem. Chem. Phys. 10, 4716 (2008)] as a reference for the undistorted monomers' geometries, a distortion correction has been added, which was taken from a former flexible-monomer ab initio potential. This correction allows us to retrieve the correct binding energy D e = 21.0 kJ mol −1 , and leads to an equilibrium geometry in close agreement with the one obtained from benchmark calculations. The kinetic energy operator describing the flexible-monomer water dimer has been expressed in terms of Radau coordinates for each monomer and a recent general cluster polyspherical formulation describing their relative motions. Within this formulation, an adiabatic scheme has been invoked in order to decouple fast (intramolecular) modes and slow (intermolecular) ones. Different levels of approximation were tested, which differ in the way in which the residual potential coupling between the intramolecular modes located on different monomers and the dependence of the monomer rotational constants on the dimer geometry are handled. Accurate calculations of the vibration-rotation-tunneling levels of (H 2 O) 2 and (D 2 O) 2 were performed, which show the best agreement with experiments achieved so far for any water potential. Intramolecular excitations of the two monomers were calculated within two limiting cases, to account for the lack of non-adiabatic coupling between intramolecular modes due to the intermolecular motion. In the first model, the excitation was assumed to stay either on the donor or the acceptor molecule, and to hop between the two moieties upon donor-acceptor interchange. In the second model, the excitation remains on the same molecule whatever is the dimer geometry. Marginal frequency differences, less than 2 cm −1 , were obtained for all modes, and the resulting infrared shifts are in good agreement with experiments.

Section: Flexible-monomer Resultsmentioning

confidence: 99%

Spectra of water dimer from a new ab initio potential with flexible monomers

Leforestier

Szalewicz

Avoird

2012

111

164

“…Such accuracies have so far only been reported for small H-bonded complexes, such as the dimers and trimers of HF, H 2 O, and HCl. [30][31][32]58 Both correlated wave function and dispersion-corrected density functional calculations predict the face and edge isomers. There are two calculated face structures, B and B ′ , with a low barrier between them; we observe only one face isomer.…”

Section: Discussionmentioning

confidence: 99%

“…29 Below, we show that both isomers are formed; we can determine the D 0 (S 0 ) values of both isomers separately within ±3 cm −1 and ±10 cm −1 , making these measurements among the most accurate experimental intermolecular dissociation energies to date. 9,[30][31][32] These measurements on isomers of the same complex represent useful benchmarks and a special challenge for theory. The accuracy of calculated dissociation energies of large intermolecular complexes depend on whether the structure is π-stacked or H-bonded.…”

Section: Introductionmentioning

confidence: 99%

Accurate dissociation energies of two isomers of the 1-naphthol⋅cyclopropane complex

Maity

Knochenmuss

Holzer

et al. 2016

Articles you may be interested inInfluences of the propyl group on the van der Waals structures of 4-propylaniline complexes with one and two argon atoms studied by electronic and cationic spectroscopy J. Chem. Phys. 143, 034308 (2015); 10.1063/1.4927004The weak hydrogen bond in the fluorobenzene-ammonia van der Waals complex: Insights into the effects of electron withdrawing substituents on π versus in-plane bonding J. Chem. Phys. 126, 154319 (2007) The 1-naphthol·cyclopropane intermolecular complex is formed in a supersonic jet and investigated by resonant two-photon ionization (R2PI) spectroscopy, UV holeburning, and stimulated emission pumping (SEP)-R2PI spectroscopy. Two very different structure types are inferred from the vibronic spectra and calculations. In the "edge" isomer, the OH group of 1-naphthol is directed towards a C-C bond of cyclopropane, the two ring planes are perpendicular. In the "face" isomer, the cyclopropane is adsorbed on one of the π-aromatic faces of the 1-naphthol moiety, the ring planes are nearly parallel. Accurate ground-state intermolecular dissociation energies D 0 were measured with the SEP-R2PI technique. The D 0 (S 0 ) of the edge isomer is bracketed as 15.35 ± 0.03 kJ/mol, while that of the face isomer is 16.96 ± 0.12 kJ/mol. The corresponding excited-state dissociation energies D 0 (S 1 ) were evaluated using the respective electronic spectral shifts. Despite the D 0 (S 0 ) difference of 1.6 kJ/mol, both isomers are observed in the jet in similar concentrations, so they must be separated by substantial potential energy barriers. Intermolecular binding energies, D e , and dissociation energies, D 0 , calculated with correlated wave function methods and two dispersion-corrected density-functional methods are evaluated in the context of these results. The density functional calculations suggest that the face isomer is bound solely by dispersion interactions. Binding of the edge isomer is also dominated by dispersion, which makes up two thirds of the total binding energy. Published by AIP Publishing. [http://dx

“…[4][5][6] In particular, bimolecular clusters encompass a variety of noncovalent bonding prototypes, ranging from pure van der Waals interactions 7 in Ar-Ar (D 0 ≈ 84 cm −1 ) to the significantly stronger hydrogen bonding in water dimer (D 0 ≈ 1105(10) cm −1 ). [8][9][10] A striking feature of these weakly bound van der Waals systems is the propensity for each component to retain a significant fraction of monomeric character, for example, as noted in the small shifts of infrared transition frequencies upon complexation. 11 Furthermore, weak potential coupling can lead to nearly free internal rotation of the dimer subunits; in Ar-H 2 O, for example, the internal rotational spacings are shifted by only a few wavenumbers 12 from those of free H 2 O.…”

Section: Introductionmentioning

confidence: 99%

Overtone vibrational spectroscopy in H2-H2O complexes: A combined high level theoretical ab initio, dynamical and experimental study

Ziemkiewicz

Pluetzer

Nesbitt

et al. 2012

First results are reported on overtone (v OH = 2 ← 0) spectroscopy of weakly bound H 2 -H 2 O complexes in a slit supersonic jet, based on a novel combination of (i) vibrationally mediated predissociation of H 2 -H 2 O, followed by (ii) UV photodissociation of the resulting H 2 O, and (iii) UV laser induced fluorescence on the nascent OH radical. In addition, intermolecular dynamical calculations are performed in full 5D on the recent ab initio intermolecular potential of Valiron et al. [J. Chem. Phys. 129, 134306 (2008)] in order to further elucidate the identity of the infrared transitions detected. Excellent agreement is achieved between experimental and theoretical spectral predictions for the most strongly bound van der Waals complex consisting of ortho (I = 1) H 2 and ortho (I = 1) H 2 O (oH 2 -oH 2 O). Specifically, two distinct bands are seen in the oH 2 -oH 2 O spectrum, corresponding to internal rotor states in the upper vibrational manifold of and rotational character. However, none of the three other possible nuclear spin modifications (pH 2 -oH 2 O, pH 2 -pH 2 O, or oH 2 -pH 2 O) are observed above current signal to noise level, which for the pH 2 complexes is argued to arise from displacement by oH 2 in the expansion mixture to preferentially form the more strongly bound species. Direct measurement of oH 2 -oH 2 O vibrational predissociation in the time domain reveals lifetimes of 15(2) ns and <5(2) ns for the and states, respectively. Theoretical calculations permit the results to be interpreted in terms of near resonant energy levels and intermolecular alignment of the H 2 and H 2 O wavefunctions, providing insight into predissociation dynamical pathways from these metastable levels.