Rotational distributions following van der Waals molecule dissociation:  Comparison between experiment and theory for benzene–Ar

Sampson, Rebecca K; Bellm, Susan; McCaffery, A. J.; Lawrance, Warren D.

doi:10.1063/1.1847512

Cited by 14 publications

(17 citation statements)

References 35 publications

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“…By contrast the VP of the benzene-Ar vdW complex from the 6 1 level occurs from a geometry well away from the c.m. of benzene 19 indicating wide amplitude in the vdW bend. The VP of rare gas-diatomic vdW molecules is also characterised by maximum b n values close to the geometric limit.…”

Section: Theoretical Analysis; the Am Modelmentioning

confidence: 98%

“…VP involving polyatomic species having more than one inertial axis introduces additional complexity. Sampson et al 19 utilised an 'equivalent rotor' method to calculate rotational distributions of benzene following VP of the benzene-Ar vdW complex. This method, introduced to calculate VRT probabilities in 6 1 benzene, was tested by comparing calculated and experimental VRT data on a range of polyatomic species and is described in greater detail in the original work.…”

Section: Theoretical Analysis; the Am Modelmentioning

confidence: 99%

“…18,23 In molecules having many vibrational modes, relaxation processes are often remarkably selective 24 in a manner that is not well understood. Sampson et al 19 suggested that transitions between vibrational states in inelastic and dissociative events require the initiating impulse to be in such a direction that the nuclear motion causing vibrational mode change additionally be capable of inducing the appropriate molecular rotation. These linked requirements constitute highly selective criteria on the nature of acceptor normal modes.…”

Section: Fragment Vibrational State Distributionsmentioning

confidence: 99%

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The mechanism of H-bond rupture: the vibrational pre-dissociation of C2H2–HCl and C2H2–DCl

Pritchard

Parr

et al. 2007

Phys. Chem. Chem. Phys.

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Pair correlated fragment rovibrational distributions are presented following vibrational predissociation of the C2H2-DCl van der Waals dimer initiated by excitation of the asymmetric (asym) C-H stretch. The only observed fragmentation pathways are DCl (v= 0; j= 6-9)+ C2H2(nu2= 1; j= 1-5). These and previously reported data on the related C2H2-HCl species are analysed using the angular momentum (AM) method. Calculations accurately reproduce fragment rovibrational distributions following dissociation of the C2H2-HCl dimer initiated either by excitation of the asym C-H stretch or via the HCl stretch, and those from C2H2-DCl initiated via asym C-H stretch excitation. The calculations demonstrate that the dimer is bent at the moment of dissociation. Several geometries are found that lead to H-bond breakage via a clearly identified set of fragment quantum states. The results suggest a hierarchy in the disposal of excess energy and angular momentum between fragment vibration, rotation and recoil. Deposition of the largest portion of energy into a C2H2 vibrational state sets an upper limit on HCl rotation, which then determines the energy and AM remaining for C2H2 rotation and fragment recoil. Acceptor C2H2 vibrational modes follow a previously noted propensity, implying that the dissociating impulse must be able to induce appropriate nuclear motions both in the acceptor vibration and in rotation of the C2H2 fragment.

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Section: Theoretical Analysis; the Am Modelmentioning

confidence: 98%

Section: Theoretical Analysis; the Am Modelmentioning

confidence: 99%

Section: Fragment Vibrational State Distributionsmentioning

confidence: 99%

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The mechanism of H-bond rupture: the vibrational pre-dissociation of C2H2–HCl and C2H2–DCl

Pritchard

Parr

et al. 2007

Phys. Chem. Chem. Phys.

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“…The model has successfully been used in various contexts, including modeling the product rotational distributions arising from vibrational predissociation of various weakly bound dimers. [60][61][62] Here, we apply it qualitatively to overtone predissociation of HCl dimer with the simplifying assumption that dissociation leads to counter rotation of the HCl monomers i.e. the orbital angular momentum of the products is equal and opposite to the difference between the rotational angular momenta for the H-bond acceptor and donor fragments:…”

Section: Correlated Product Pair Distributions the Ion Imaging Measurements Characterize 22 Distinctmentioning

confidence: 99%

Mode-specific vibrational predissociation dynamics of (HCl)2 via the free and bound HCl stretch overtones

Kapnas

Murray

2020

The Journal of Chemical Physics

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Velocity-map ion imaging has been used to study the vibrational predissociation dynamics of HCl dimer following IR excitation in the HCl stretch overtone region near 1.77 Å. HCl monomer predissociation products were detected state-selectively using 2+1 resonance-enhanced multiphoton ionization spectroscopy. The IR action spectrum show the free HCl stretch (2ν1), the bound HCl stretch (2ν2), and a combination band involving the intermolecular van der Waals stretching mode (2ν2+ν4). Fragment speed distributions extracted from ion images obtained for a range of HCl(v = 0, 1; J) levels following vibrational excitation on the 2ν1 and 2ν2 bands yield the correlated product pair distributions. All product pairs comprise HCl(v = 1) + HCl(v = 0) and show a strong propensity to minimize the recoil kinetic energy. Highly non-statistical and mode-dependent HCl product rotational distributions are observed, in contrast to that observed following stretch fundamental excitation. Predissociation lifetimes are also mode-dependent: excitation of the free HCl leads to τVP = 13±1 ns, while the bound stretch has a shorter lifetime τVP ≤ 6 ns. The dimer dissociation energy determined from energy conservation, D0 = 397±7 cm -1 , is slightly smaller than previously reported values. The results are discussed in the context of previous observations for (HF)2 and (HCl)2 after excitation of HX stretch fundamentals and models for vibrational predissociation.

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“…20,25 It appears that this is also the case for dissociation of pDFB-H 2 O complexes. Consider dissociation from 3 1 .…”

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confidence: 97%

A velocity map ion imaging study of difluorobenzene-water complexes: Binding energies and recoil distributions

Bellm

Leeuwen

Lawrance

2008

The Journal of Chemical Physics

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The binding energies of the p-, m-, and o-difluorobenzene-H2O complexes have been measured by velocity map ion imaging to be 922±10, 945±10, and 891±4cm−1, respectively. The lack of variation provides circumstantial evidence for water binding to the three isomers via the same interaction, viz. an in-plane O–H⋯F hydrogen bond to one of the fluorine atoms on the ring, with a second, weaker interaction of the water O atom with an ortho hydrogen, as determined previously for the p-difluorobenzene-H2O complex [Kang et al., J. Phys. Chem. A 109, 767 (2005)]. The ground state binding energies for the difluorobenzene-H2O complexes are ∼5%–11% larger than that for benzene-H2O, where binding occurs to the π electrons out-of-plane. However, in the S1 state the binding energies of the o- and p-difluorobenzene-H2O complexes are smaller than the benzene-H2O value, raising an interesting question about whether the geometry at the global energy minimum remains in-plane in the excited electronic states of these two complexes. Recoil energy distributions for dissociation of p-difluorobenzene-H2O have been measured from the 31¯, 52¯, and 3151¯ levels of the excited electronic state. These levels are 490, 880, and 1304cm−1, respectively, above the dissociation threshold. Within the experimental uncertainty, the recoil energy distributions are the same for dissociation from these three states, with average recoil energies of ∼100cm−1. These recoil energies are 60% larger than was observed for the dissociation of p-difluorobenzene-Ar, which is a substantially smaller increase than the 400% seen in a comparable study of dissociation within the triplet state for pyrazine-Ar, -H2O complexes. The majority of the available energy is partitioned into vibration and rotation of the fragments.

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Rotational distributions following van der Waals molecule dissociation: Comparison between experiment and theory for benzene–Ar

Cited by 14 publications

References 35 publications

The mechanism of H-bond rupture: the vibrational pre-dissociation of C2H2–HCl and C2H2–DCl

The mechanism of H-bond rupture: the vibrational pre-dissociation of C2H2–HCl and C2H2–DCl

Mode-specific vibrational predissociation dynamics of (HCl)2 via the free and bound HCl stretch overtones

A velocity map ion imaging study of difluorobenzene-water complexes: Binding energies and recoil distributions

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