| 1. |
- Andersen, J, et al.
(författare)
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Communication: THz absorption spectrum of the CO2-H2O complex: Observation and assignment of intermolecular van der Waals vibrations.
- 2014
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 140:9
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Tidskriftsartikel (refereegranskat)abstract
- Terahertz absorption spectra have been recorded for the weakly bound CO2-H2O complex embedded in cryogenic neon matrices at 2.8 K. The three high-frequency van der Waals vibrational transitions associated with out-of-plane wagging, in-plane rocking, and torsional motion of the isotopic H2O subunit have been assigned and provide crucial observables for benchmark theoretical descriptions of this systems' flat intermolecular potential energy surface. A (semi)-empirical value for the zero-point energy of 273 ± 15 cm(-1) from the class of intermolecular van der Waals vibrations is proposed and the combination with high-level quantum chemical calculations provides a value of 726 ± 15 cm(-1) for the dissociation energy D0.
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| 2. |
- Andersen, J., et al.
(författare)
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Competition between weak OH·π and CH·O hydrogen bonds : THz spectroscopy of the C2H2 - H2O and C2H4 - H2O complexes
- 2017
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 146:19
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Tidskriftsartikel (refereegranskat)abstract
- THz absorption spectra have been recorded for the weakly bound molecular complexes of H2O with C2H4 and C2H2 embedded in cryogenic neon matrices at 2.8 K. The observation and assignment of a large-amplitude acceptor OH librational mode of the C2H2 - H2O complex at 145.5 cm−1 confirms an intermolecular CH⋯O hydrogen-bonded configuration of C2v symmetry with the H2O subunit acting as the hydrogen bond acceptor. The observation and assignment of two large-amplitude donor OH librational modes of the C2H4 - H2O complex at 255.0 and 187.5 cm−1, respectively, confirms an intermolecular OH⋯π hydrogen-bonded configuration with the H2O subunit acting as the hydrogen bond donor to the π-cloud of C2H4. A (semi)-empirical value for the change of vibrational zero-point energy of 4.0-4.1 kJ mol−1 is proposed and the combination with quantum chemical calculations at the CCSD(T)-F12b/aug-cc-pVQZ level provides a reliable estimate of 7.1 ± 0.3 kJ mol−1 for the dissociation energy D0 of the C2H4 - H2O complex. In addition, tentative assignments for the two strongly infrared active OH librational modes of the ternary C2H4 - HOH - C2H4 complex having H2O as a doubly OH·π hydrogen bond donor are proposed at 213.6 and 222.3 cm−1. The present findings demonstrate that the relative stability of the weak hydrogen bond motifs is not entirely rooted in differences of electronic energy but also to a large extent by differences in the vibrational zero-point energy contributions arising from the class of large-amplitude intermolecular modes.
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| 3. |
- Andersen, J., et al.
(författare)
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Far-Infrared Investigation of the Benzene-Water Complex : The Identification of Large-Amplitude Motion and Tunneling Pathways
- 2020
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 124:3, s. 513-519
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Tidskriftsartikel (refereegranskat)abstract
- The far-infrared spectrum of the weakly OH···πhydrogen-bonded benzene-water complex has been studied in neon and argon matrices, below 30 K. The in-plane water libration has been observed in both neon and argon for H2O and D2O complexed with C6H6 and C6D6 but not for the corresponding complexes involving HDO. Both H2O and D2O can tunnel between the two possible hydrogen bonds. This is not possible for HDO. The reported far-infrared observations have implications for the interpretation of the previously obtained molecular beam microwave spectrum of the benzene-water complex.
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| 4. |
- Andersen, J, et al.
(författare)
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Spectroscopic identification of ethanol-water conformers by large-amplitude hydrogen bond librational modes.
- 2015
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 143:22
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Tidskriftsartikel (refereegranskat)abstract
- The far-infrared absorption spectra have been recorded for hydrogen-bonded complexes of water with ethanol embedded in cryogenic neon matrices at 2.8 K. The partial isotopic H/D-substitution of the ethanol subunit enabled by a dual inlet deposition procedure enables the observation and unambiguous assignment of the intermolecular high-frequency out-of-plane and the low-frequency in-plane donor OH librational modes for two different conformations of the mixed binary ethanol/water complex. The resolved donor OH librational bands confirm directly previous experimental evidence that ethanol acts as the O⋯HO hydrogen bond acceptor in the two most stable conformations. In the most stable conformation, the water subunit forces the ethanol molecule into its less stable gauche configuration upon dimerization owing to a cooperative secondary weak O⋯HC hydrogen bond interaction evidenced by a significantly blue-shift of the low-frequency in-plane donor OH librational band origin. The strong correlation between the low-frequency in-plane donor OH librational motion and the secondary intermolecular O⋯HC hydrogen bond is demonstrated by electronic structure calculations. The experimental findings are further supported by CCSD(T)-F12/aug-cc-pVQZ calculations of the conformational energy differences together with second-order vibrational perturbation theory calculations of the large-amplitude donor OH librational band origins.
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| 5. |
- Andersen, J., et al.
(författare)
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The influence of large-amplitude librational motion on the hydrogen bond energy for alcohol-water complexes
- 2015
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 17:37, s. 23761-23769
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Tidskriftsartikel (refereegranskat)abstract
- The far-infrared absorption spectra have been recorded for hydrogen-bonded complexes of water with methanol and t-butanol embedded in cryogenic neon matrices at 2.8 K. The partial isotopic substitution of individual subunits enabled by a dual inlet deposition procedure provides for the first time unambiguous assignments of the intermolecular high-frequency out-of-plane and low-frequency in-plane donor OH librational modes for mixed alcohol-water complexes. The vibrational assignments confirm directly that water acts as the hydrogen bond donor in the most stable mixed complexes and the tertiary alcohol is a superior hydrogen bond acceptor. The class of large-amplitude donor OH librational motion is shown to account for up to 5.1 kJ mol(-1) of the destabilizing change of vibrational zero-point energy upon intermolecular OH center dot center dot center dot O hydrogen bond formation. The experimental findings are supported by complementary electronic structure calculations at the CCSD(T)-F12/aug-cc-pVTZ level of theory.
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| 6. |
- Kollipost, F, et al.
(författare)
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The effect of hydrogen bonding on torsional dynamics: A combined far-infrared jet and matrix isolation study of methanol dimer.
- 2014
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 141:17
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Tidskriftsartikel (refereegranskat)abstract
- The effect of strong intermolecular hydrogen bonding on torsional degrees of freedom is investigated by far-infrared absorption spectroscopy for different methanol dimer isotopologues isolated in supersonic jet expansions or embedded in inert neon matrices at low temperatures. For the vacuum-isolated and Ne-embedded methanol dimer, the hydrogen bond OH librational mode of the donor subunit is finally observed at ∼560 cm(-1), blue-shifted by more than 300 cm(-1) relative to the OH torsional fundamental of the free methanol monomer. The OH torsional mode of the acceptor embedded in neon is observed at ∼286 cm(-1). The experimental findings are held against harmonic predictions from local coupled-cluster methods with single and double excitations and a perturbative treatment of triple excitations [LCCSD(T)] and anharmonic. VPT2 corrections at canonical MP2 and density functional theory (DFT) levels in order to quantify the contribution of vibrational anharmonicity for this important class of intermolecular hydrogen bond vibrational motion.
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| 7. |
- Larsen, R. Wugt, et al.
(författare)
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High-resolution infrared study of collisionally cooled trans-1,2-dichloroethylene
- 2007
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Ingår i: Journal of Molecular Spectroscopy. - : Elsevier BV. - 0022-2852. ; 243:1, s. 99-102
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Tidskriftsartikel (refereegranskat)abstract
- A recently constructed long-path enclosive flow cooling apparatus is employed to obtain the Fourier transform gas-phase infrared absorption spectrum of natural isotopic trans-1,2-dichloroethylene with a resolution of 0.00190 cm(-1) in the 800-1000 cm(-1) spectral region. The rotational structure of the out-of-plane CH flapping fundamental has been analyzed for the isotopic analogues Cl-35(2) and (ClCl)-Cl-35-Cl-37 using the Watson A-reduced Hamiltonian model and I-r-representation. A ground-state combination difference analysis for the (ClCl)-Cl-35-Cl-37 isotopomer based on 1402 assigned transitions belonging to the v(6) band yields a band origin of 897.94493(10) cm(-1) and values for the ground-state rotational constants: A(0) = 1.7466454(44) cm(-1), B-0 = 0.05019643(82) cm(-1) and C-0 = 0.04877977(82) cm(-1) together with quartic centrifugal distortion constants. The red-shift of 0.00444(10) cm(-1) observed for the v(6) band origin of (ClCl)-Cl-35-Cl-37 relative to the Cl-35(2), band origin is now consistent with the Rayleigh rule. (c) 2007 Elsevier Inc. All rights reserved.
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