Structure and vibrational dynamics of the benzene dimer

Špirko, V.; Engkvist, Ola; Soldán, Pavel; Selzle, H. L.; Schlag, E. W.; Hobza, Pavel

doi:10.1063/1.479338

Cited by 143 publications

(128 citation statements)

References 40 publications

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“…Of these four tunneling motions, if cap turnover tunneling were not observable, then the molecular symmetry Table 2 Irreducible representations G of the FCT group G 576 , with their dimension n G , and of the subgroup D 6 (M) A # D 6 (M) B and the corresponding nuclear spin statistical weights. The superscripts AE refer to the inversion, E*, symmetry group would be the group G 144 = C 6v (M) cap # D 6 (M) stem considered before by Spirko et al 31 The symmetry adaptation of the basis, explained in section IVB, ensures that the calculated VRT states carry the irreps of the FCT group G 576 . The particular molecular symmetry group corresponding to the calculated level splitting pattern, can be determined via subduction of the G 576 irreps along different subgroup chains.…”

Section: Symmetrymentioning

confidence: 99%

Vibration–rotation-tunneling states of the benzene dimer: an ab initio study

Avoird

Podeszwa

Szalewicz

et al. 2010

Phys. Chem. Chem. Phys.

152

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An improved intermolecular potential surface for the benzene dimer is constructed from interaction energies computed by symmetry-adapted perturbation theory, SAPT(DFT), with the inclusion of third-order contributions. Twelve characteristic points on the surface have been investigated also using the coupled-cluster method with single, double, and perturbative triple excitations, CCSD(T), and triple-zeta quality basis sets with midbond functions. The SAPT and CCSD(T) results are in close agreement and provide the best representation of these points to date. The potential was used in calculations of vibration-rotation-tunneling (VRT) levels of the dimer by a method appropriate for large amplitude intermolecular motions and tunneling between multiple equivalent minima in the potential. The resulting VRT levels were analyzed with the use of the permutation-inversion full cluster tunneling (FCT) group G 576 and a chain of subgroups that starts from the molecular symmetry group C s (M) of the rigid dimer at its equilibrium C s geometry and leads to G 576 if all possible intermolecular tunneling mechanisms are feasible. Further information was extracted from the calculated wave functions. It was found, in agreement with the experimental data, that for all of the 54 G 576 symmetry species (with different nuclear spin statistical weights) the lower VRT states have a tilted T-shape (TT) structure; states with the parallel-displaced structure are higher in energy than the ground state of A + 1 symmetry by at least 30 cm À1 . The dissociation energy D 0 equals 870 cm À1 , while the depth D e of the TT minimum in the potential is 975 cm À1 . Hindered rotation of the cap in the TT structure and tilt tunneling lead to level splittings on the order of 1 cm À1 . Also intermolecular vibrations with excitation energies starting at a few cm À1 were identified. A further small, but probably significant, level splitting was assigned to cap turnover, although in scans of the potential surface we could not find a plausible 'reaction path' for this process. Rotational constants were extracted from energy levels calculated for total angular momentum J = 0 and 1, and from expectation values of the inertia tensor. Although the end-over-end rotational constant B + C agrees well with the measured microwave spectra, there is disagreement with the measurements concerning the (a)symmetric rotor character of the benzene dimer. It is concluded from calculations for the 54 nuclear spin species that the microwave spectrum should show overlapping contributions from many different species. Another interesting conclusion regards the role of the quantum number K, for a prolate near-symmetric rotor the projection of the total angular momentum on the prolate axis. For the benzene dimer, K has a substantial effect on the energy levels associated with the intermolecular motions of the complex.

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Section: Symmetrymentioning

confidence: 99%

Vibration–rotation-tunneling states of the benzene dimer: an ab initio study

Avoird

Podeszwa

Szalewicz

et al. 2010

Phys. Chem. Chem. Phys.

152

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“…Benzene dimer has been extensively studied theoretically [15] and experimentally [16,17]. Theoretical studies find two stable isomers, one having a T-shaped or perpendicular geometry and the other a stacked parallel structure in which the monomers are displaced from the eclipsed conformation [15].…”

Section: Introductionmentioning

confidence: 99%

“…Theoretical studies find two stable isomers, one having a T-shaped or perpendicular geometry and the other a stacked parallel structure in which the monomers are displaced from the eclipsed conformation [15]. The T-shaped isomer is the global minimum on the shallow potential surface.…”

Section: Introductionmentioning

confidence: 99%

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Effects of cluster formation on spectra of benzo[a]pyrene and benzo[e]pyrene

Fioressi

Binning

Bacelo

2008

Chemical Physics Letters

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Absorption and fluorescence emission spectra of the polycyclic aromatic hydrocarbons benzo [a] pyrene (BaP) and benzo[e]pyrene (BeP) in solution and adsorbed on silica have been obtained and compared to examine the spectroscopic effects of clustering. Molecular mechanics calculations with the UFF potential were done to optimize monomer, dimer and trimer geometries, and energy differences were determined by MP2/6-31G* calculations. Fluorescence emission spectra of adsorbed BeP and BaP display a red shift that progresses with increased loading, and the two differ in their photodegradation kinetics. The experimental and theoretical results are found to be consistent.

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“…3 and 4. undertook detailed spectroscopic studies of (Bz-h 6 ) 2 , the (Bz-h 6 )(Bz-d 6 ) heterodimer, the fully deuterated homodimer (Bz-d 6 ) 2 , and of other D-and 13 C-isotopomers of (Bz) 2 , attempting to determine the excitonic splitting between the S 0 → S 1 and S 0 → S 2 origins of (Bz) 2 , as well as the excited-state structure of (Bz) 2 . 10,12 Combining the spectroscopic results with early high-level ab initio calculations of (Bz) 2 , Schlag, Hobza, and co-workers concluded that the (Bz) 2 structure is T-shaped, 10,12,24,25 in good agreement with the later microwave structure. 2 They interpreted a ∼2 cm −1 splitting of the 0 0 0 band of (Bz) 2 as arising from the excitonic S 1 /S 2 splitting.…”

Section: Molecular-beam Electric-deflection Measurements Bymentioning

confidence: 50%

The elusive S2 state, the S1/S2 splitting, and the excimer states of the benzene dimer

Balmer

Trachsel

Avoird

et al. 2015

The Journal of Chemical Physics

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We observe the weak S 0 → S 2 transitions of the T-shaped benzene dimers (Bz) 2 and (Bz-d 6 ) 2 about 250 cm −1 and 220 cm −1 above their respective S 0 → S 1 electronic origins using two-color resonant two-photon ionization spectroscopy. Spin-component scaled (SCS) second-order approximate coupled-cluster (CC2) calculations predict that for the tipped T-shaped geometry, the S 0 → S 2 electronic oscillator strength f el (S 2 ) is ∼10 times smaller than f el (S 1 ) and the S 2 state lies ∼240 cm −1 above S 1 , in excellent agreement with experiment. The S 0 → S 1 (ππ * ) transition is mainly localized on the "stem" benzene, with a minor stem → cap charge-transfer contribution; the S 0 → S 2 transition is mainly localized on the "cap" benzene. The orbitals, electronic oscillator strengths f el (S 1 ) and f el (S 2 ), and transition frequencies depend strongly on the tipping angle ω between the two Bz moieties. The SCS-CC2 calculated S 1 and S 2 excitation energies at different T-shaped, stacked-parallel and parallel-displaced stationary points of the (Bz) 2 ground-state surface allow to construct approximate S 1 and S 2 potential energy surfaces and reveal their relation to the "excimer" states at the stacked-parallel geometry. The f el (S 1 ) and f el (S 2 ) transition dipole moments at the C 2v -symmetric T-shape, parallel-displaced and stacked-parallel geometries are either zero or ∼10 times smaller than at the tipped T-shaped geometry. This unusual property of the S 0 → S 1 and S 0 → S 2 transition-dipole moment surfaces of (Bz) 2 restricts its observation by electronic spectroscopy to the tipped and tilted T-shaped geometries; the other ground-state geometries are impossible or extremely difficult to observe. The S 0 → S 1 /S 2 spectra of (Bz) 2 are compared to those of imidazole · (Bz) 2 , which has a rigid triangular structure with a tilted (Bz) 2 subunit. The S 0 → S 1 / S 2 transitions of imidazole-(benzene) 2 lie at similar energies as those of (Bz) 2 , confirming our assignment of the (Bz) 2 S 0 → S 2 transition. C 2015 AIP Publishing LLC. [http://dx

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Structure and vibrational dynamics of the benzene dimer

Cited by 143 publications

References 40 publications

Vibration–rotation-tunneling states of the benzene dimer: an ab initio study

Vibration–rotation-tunneling states of the benzene dimer: an ab initio study

Effects of cluster formation on spectra of benzo[a]pyrene and benzo[e]pyrene

The elusive S2 state, the S1/S2 splitting, and the excimer states of the benzene dimer

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