Observation of high-lying vibrational predissociation states of H+5

Bae, Young K.

doi:10.1016/0009-2614(91)87137-z

Cited by 30 publications

(45 citation statements)

References 7 publications

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“…Beside, infrared spectroscopic H 5 + +hω → H 3 + + H 2 measurements [4][5][6] provide information about the H 5 + complex structure, energetics, and fragmentation dynamics. This last process can be viewed as a half collision, allowing a complementary study of the density of states involved in full collisions.…”

Section: The Hmentioning

confidence: 99%

“…The delocalized and highly anharmonic shared-proton stretch mode was shown to carry very large oscillator strength, its excitation playing a major role in the assignment of experimental spectral features of H 5 + and D 5 + cations [6]. To date, several full dimensional potential energy surfaces (PESs) for H 5 + are available [8][9][10].…”

Section: The Hmentioning

confidence: 99%

“…To date, several full dimensional potential energy surfaces (PESs) for H 5 + are available [8][9][10]. In this Rapid Communication we use the accurate triatomics in molecules based analytical PES [9], fitted to high-level ab initio points [11], together with the electric dipole moment surface recently reported and used to perform spectra simulations at zero temperature [12].…”

Section: The Hmentioning

confidence: 99%

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Infrared spectrum of H5+and D5+: The simplest shared-proton model

et al. 2011

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We present a two-dimensional collinear, adiabatic model to describe the motion of a proton in between two hydrogen molecules which adjust their elongation to trace a minimum-energy path. Together with bound states, the predissociative, vibrationally excited states involved in the electric dipole transitions are characterized. The main qualitative features of the infrared spectra of H 5 + and its deuterated variant are discussed, and the effect of the temperature of the clusters is analyzed. To just account for the proton transfer between the two H 2 moieties, we present an extremely simplified two-dimensional (2D) model which incorporates the effect of the temperature.Considering three collinear masses M 1 -M 0 -M 2 , denoting by d 1 and d 2 , the distances from the central mass to the extreme ones, and employing the coordinates R = d 1 + d 2 (0 R ∞) and r = d 1 − d 2 (−R r R) the kinetic energy operator in the center of mass system becomeŝ

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Section: The Hmentioning

confidence: 99%

Section: The Hmentioning

confidence: 99%

Section: The Hmentioning

confidence: 99%

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Infrared spectrum of H5+and D5+: The simplest shared-proton model

et al. 2011

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“…On the other hand, the CID studies have revealed patterns for the cluster dissociation and their dependence on the shell structure of H 2 distribution. Hitherto, very few theoretical and experimental attention has been payed to the vibrational properties and the infrared spectra of the hydrogen clusters, these studies being basically restricted to the H + 5 species [38,39]. For clusters larger than the H + 5 one, only a few experimental results are available [42] and the theoretical calculations have been limited to the harmonics frequencies [14,40,41].…”

Section: Introductionmentioning

confidence: 99%

On the formation mechanisms of hydrogen ionic clusters

Barbatti¹,

Nascimento²

2003

Braz. J. Phys.

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Structural and thermodynamic properties of hydrogen molecular clusters formed around an atomic or molecular cation are examined. The shell distribution of H2 molecules and the size of the clusters are discussed. The Bloom-Margenau model for predicting the number of neutral molecules that could bind to a cation core is investigated and its limitations are illustrated using the Li + (H2) k clusters as test case. Finally, results for the entropy of the H + n clusters (n = 5 − 27, odd) and for the Gibbs free energy variations associated to the cluster formation are presented and the spontaneity of the clustering process in different conditions is examined. I IntroductionThe presence of a cation in a molecular hydrogen environment leads to the formation of molecular clusters around the ion. In the case of an H 2 homogeneous atmosphere, an H + 2 ion is quickly converted to the H + 3 molecule, which becomes the core for the clustering processwhere the exceeding H 2 molecule carries away the excess of energy, stabilizing the cluster. From these multiple-steps reactions, H + n clusters (n odd) are formed, and clusters as large as H + 99 have been observed [1]. Depending on the temperature and pressure conditions, the H + 15 and H + 17 clusters are the more abundant.One of the most interesting features of these species is that in the cluster, each H 2 molecule is strongly bound by the coulombian field of the cation. This may be very useful when dealing with hydrogen storage problems.In the last decade, ab initio calculations have been performed to clusters as large as H + 35 [2][3][4][5][6][7][8][9][10][11][12]. Recently, more attention has been dedicated to the H + 5 cluster. Its potential energy surface has been studied at high levels of calculation [13,14] and its presence in some interstellar environments in concentrations up two times higher than that of the H + 3 molecule has been investigated [15].Besides the H + 3 molecular ion, a large variety of atomic and molecular cations has been considered as a core for H 2 clustering: the first-column Li + , Na + and K + ions [16][17][18][19][20][21][22] Table I summarizes some properties of these X + (H 2 ) k hydrogen clusters.The experimental work on the hydrogen clusters has been concentrated on enthalpy variation measurements (∆H) [16,24,25,26,31,33] and collisional induced dissociation (CID) studies [34,35,36,37]. The ∆H measurements for the H + n clusters and for the most general X + (H 2 ) k clusters have been an important source of information about the cluster energetic properties and have guided the theoretical studies. On the other hand, the CID studies have revealed patterns for the cluster dissociation and their dependence on the shell structure of H 2 distribution. Hitherto, very few theoretical and experimental attention has been payed to the vibrational properties and the infrared spectra of the hydrogen clusters, these studies being basically restricted to the H + 5 species [38,39]. For clusters larger than the H + 5 one, only a few experimental results are...

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“…64 These resonances close to the dissociation threshold are accessible by infrared excitation from the H + 5 , and there are several experimental results on this system and its isotopic variants. [59][60][61]65 If the hypothesis discussed above is true, there may be some differences in the broadening of the resonances near the dissociation threshold as a function of the total angular momentum excitation, and this could be probably measured by changing the experimental rotational temperature of the experiments. Also, there have been several theoretical simulations on this infrared predissociation spectra, 44,61,62 but they use either approximate methods or reduced dimensionality models which need to be improved to account for the narrow resonances at high J with enough accuracy to extract information relevant for the transition between statistical and direct regimes in the collisions discussed in this work.…”

Section: F Rate Constantsmentioning

confidence: 99%

Dynamically biased statistical model for the ortho/para conversion in the ${\rm H}_2 + {\rm H}_3^+$H2+H3+ → ${\rm H}_3^{+} +$H3++ H2 reaction

Gómez-Carrasco

González-Sánchez

Aguado

et al. 2012

The Journal of Chemical Physics

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In this work we present a dynamically biased statistical model to describe the evolution of the title reaction from statistical to a more direct mechanism, using quasi-classical trajectories (QCT). The method is based on the one previously proposed by Park and Light [J. Chem. Phys. 126, 044305 (2007)]. A recent global potential energy surface is used here to calculate the capture probabilities, instead of the long-range ion-induced dipole interactions. The dynamical constraints are introduced by considering a scrambling matrix which depends on energy and determine the probability of the identity/hop/exchange mechanisms. These probabilities are calculated using QCT. It is found that the high zero-point energy of the fragments is transferred to the rest of the degrees of freedom, what shortens the lifetime of H + 5 complexes and, as a consequence, the exchange mechanism is produced with lower proportion. The zero-point energy (ZPE) is not properly described in quasiclassical trajectory calculations and an approximation is done in which the initial ZPE of the reactants is reduced in QCT calculations to obtain a new ZPE-biased scrambling matrix. This reduction of the ZPE is explained by the need of correcting the pure classical level number of the H + 5 complex, as done in classical simulations of unimolecular processes and to get equivalent quantum and classical rate constants using Rice-Ramsperger-Kassel-Marcus theory. This matrix allows to obtain a ratio of hop/exchange mechanisms, α(T), in rather good agreement with recent experimental results by Crabtree et al. [J. Chem. Phys. 134, 194311 (2011)] at room temperature. At lower temperatures, however, the present simulations predict too high ratios because the biased scrambling matrix is not statistical enough. This demonstrates the importance of applying quantum methods to simulate this reaction at the low temperatures of astrophysical interest.

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Observation of high-lying vibrational predissociation states of H+5

Cited by 30 publications

References 7 publications

Infrared spectrum of H5+and D5+: The simplest shared-proton model

Infrared spectrum of H5+and D5+: The simplest shared-proton model

On the formation mechanisms of hydrogen ionic clusters

Dynamically biased statistical model for the ortho/para conversion in the ${\rm H}_2 + {\rm H}_3^+$H2+H3+ → ${\rm H}_3^{+} +$H3++ H2 reaction

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