Vibrational Energy Transfer In Collisions Research Articles

Vibrational energy transfer in collisions of molecules with metal surfaces.

The Born-Oppenheimer approximation (BOA), which serves as the basis for our understanding of chemical bonding, reactivity and dynamics, is routinely violated for vibrationally inelastic scattering of molecules at metal surfaces. The title-field therefore represents a fascinating challenge to our conventional wisdom calling for new concepts that involve explicit electron dynamics occurring in concert with nuclear motion. Here, we review progress made in this field over the last decade, which has witnessed dramatic advances in experimental methods, thereby providing a much more extensive set of diverse observations than has ever before been available. We first review the experimental methods used in this field and then provide a systematic tour of the vast array of observations that are currently available. We show how these observations - taken together and without reference to computational simulations - lead us to a simple and intuitive picture of BOA failure in molecular dynamics at metal surfaces, one where electron transfer between the molecule and the metal plays a preeminent role. We also review recent progress made in the theory of electron transfer mediated BOA failure in molecule-surface interactions, describing the most important methods and their ability to reproduce experimental observation. Finally, we outline future directions for research and important unanswered questions.

Cold Collisions of Ro-Vibrationally Excited D2 Molecules.

The H2 + H2 system has long been considered a benchmark system for ro-vibrational energy transfer in bimolecular collisions. However, most studies thus far have focused on collisions involving H2 molecules in the ground vibrational level or in the first excited vibrational state. While H2 + H2/HD collisions have received wide attention due to the important role they play in astrophysics, D2 + D2 collisions have received much less attention. Recently, Zhou et al. [ Nat. Chem. 2022, 14, 658-663, DOI: 10.1038/s41557-022-00926-z] examined stereodynamic aspects of rotational energy transfer in collisions of two aligned D2 molecules prepared in the v = 2 vibrational level and j = 2 rotational level. Here, we report quantum calculations of rotational and vibrational energy transfer in collisions of two D2 molecules prepared in vibrational levels up to v = 2 and identify key resonance features that contribute to the angular distribution in the experimental results of Zhou et al. The quantum scattering calculations were performed in full dimensionality and using the rigid-rotor approximation using a recently developed highly accurate six-dimensional potential energy surface for the H4 system that allows descriptions of collisions involving highly vibrationally excited H2 and its isotopologues.

Three-dimensional analytic probabilities of coupled vibrational-rotational-translational energy transfer for DSMC modeling of nonequilibrium flows

A three-dimensional, nonperturbative, semiclassical analytic model of vibrational energy transfer in collisions between a rotating diatomic molecule and an atom, and between two rotating diatomic molecules (Forced Harmonic Oscillator–Free Rotation model) has been extended to incorporate rotational relaxation and coupling between vibrational, translational, and rotational energy transfer. The model is based on analysis of semiclassical trajectories of rotating molecules interacting by a repulsive exponential atom-to-atom potential. The model predictions are compared with the results of three-dimensional close-coupled semiclassical trajectory calculations using the same potential energy surface. The comparison demonstrates good agreement between analytic and numerical probabilities of rotational and vibrational energy transfer processes, over a wide range of total collision energies, rotational energies, and impact parameter. The model predicts probabilities of single-quantum and multi-quantum vibrational-rotational transitions and is applicable up to very high collision energies and quantum numbers. Closed-form analytic expressions for these transition probabilities lend themselves to straightforward incorporation into DSMC nonequilibrium flow codes.

Collisional energy transfer of highly excited polyatomic molecules as a stochastic process

Collisional energy transfer between highly excited molecules and bath gas is considered as a stochastic process occurring in energy space. It is assumed that the density of vibrational states of polyatomic molecules is energy-dependent. An exact solution to the master equation for conditional probability density is given in terms of simple analytical formulas for weak and strong collisions. The bulk-average moments of internal energy and the average moments of energy transfer are calculated analytically. The place occupied by the collisional transfer of vibrational energy among other stochastic processes is discussed.

Full-dimensional quantum dynamics calculations of H2–H2 collisions

We report quantum dynamics calculations of rotational and vibrational energy transfer in collisions between two para-H(2) molecules over collision energies spanning from the ultracold limit to thermal energies. Results obtained using a recent full-dimensional H(2)-H(2) potential energy surface (PES) developed by Hinde [J. Chem. Phys. 128, 154308 (2008)] are compared with those derived from the Boothroyd, Martin, Keogh, and Peterson (BMKP) PES [J. Chem. Phys. 116, 666 (2002)]. For vibrational relaxation of H(2)(v=1,j=0) by collisions with H(2)(v=0,j=0) as well as rotational excitations in collisions between ground state H(2) molecules, the PES of Hinde is found to yield results in better agreement with available experimental data. A highly efficient near-resonant energy transfer mechanism that conserves internal rotational angular momentum and was identified in our previous study of the H(2)-H(2) system [Phys. Rev. A 77, 030704(R) (2008)] using the BMKP PES is also found to be reproduced by the Hinde PES, demonstrating that the process is largely insensitive to the details of the PES. In the absence of the near-resonance mechanism, vibrational relaxation is driven by the anisotropy of the potential energy surface. Based on a comparison of results obtained using the Hinde and BMKP PESs with available experimental data, it appears that the Hinde PES provides a more accurate description of rotational and vibrational transitions in H(2)-H(2) collisions, at least for vibrational quantum numbers v ≤ 1.

Isotopically selective collisional vibrational energy transfer in CF3H

The authors investigate here the mechanism of collisionally enhanced isotopic selectivity observed in infrared multiple photon dissociation (IRMPD) of vibrationally preexcited CF3H by Boyarkin et al. [J. Chem. Phys. 118, 93 (2003)]. For both the carbon-12 and carbon-13 isotopic species they measure the dependence of the IRMPD yield on the time delay between the preexcitation and the dissociation pulses at different dissociation frequencies as well as its dependence on the initial isotopic composition of the sample. The results reveal that the collisional increase in isotopic selectivity originates not only from that of IRMPD itself but also from the isotopic selectivity of vibrational energy transfer, with the latter making the major contribution under their experimental conditions. They suggest that the observed isotopic selectivity in collisional energy transfer arises from the difference in overlap between the absorption spectra of the nu5 mode in the 12CF3H acceptor molecule with emission spectra of the same mode in the two isotopically different donors. Understanding the origin of this collisional effect has important implications for optimization of laser isotope separation processes.

Dynamically based fitting law for cross-sections of vibrational energy transfer

A three-dimensional semiclassical analytical model for cross-sections of vibrational energy transfer in collisions between an atom and a diatomic molecule has been developed. The model is based on the Bessel uniform approximation for transition probabilities valid for highly excited states of a molecule represented by the Morse oscillator. Three fitting parameters of the model are expressed in terms of the features characterizing the anisotropic intermolecular potential. The accuracy and validity of this law are tested by comparison with large Δn transitions and isotope effects in the crossed beam inelastic scattering of I2 from He, H2 and D2.

Influence of short-and long-range interaction forces on the efficiency of collisional vibrational energy transfer in the vibrational quasi-continuum

Based on measurements of the time-resolved delayed fluorescence, the influence of universal interactions on the collisional vibrational energy transfer is studied in mixtures of vibrationally excited polyatomic molecules (acetophenone, benzophenone, and anthraquinone) with inert bath gases (Ar, C2H4, SF6, CCl4, and C5H12). From the dependences of the decay rates of delayed fluorescence on bath gas pressure, the efficiencies of the establishment of vibrational (V-V relaxation) and thermal (V-T relaxation) equilibrium after excitation of molecules into the vibrational quasi-continuum of a triplet state are estimated. The main emphasis is on studying the dependences of the efficiency of collisional vibrational energy transfer on temperature and the molecular characteristics of collision partners. It is found that the efficiency increases with the complication of the structure of bath gases for the V-V process and decreases upon the increasing of their mass for the V-T process. For the temperature range 273–553 K, the negative temperature dependence of the V-V transfer probability and the positive (Landau-Teller) dependence of the V-T transfer probability were obtained. It is concluded that the above regularities reflect the dominant role of long-range attractive forces in initiating the quasi-resonant V-V transfer and of short-range repulsive forces in the V-T transfer of vibrational energy.

Temperature Dependence of the Efficiency of Collisional Transfer of Vibrational Energy in Mixtures of Vibrationally Excited Triplet Molecules with Foreign Gases

By the pressure dependences of the decay rates of delayed fluorescence activated by vibrational excitation of triplet molecules of benzophenone and anthraquinone, the efficiencies of collisional transfer of vibrational energy (V–V-transfer) in the vibrational quasi-continuum of the triplet state have been estimated. It is shown that the efficiencies of the process in mixtures with foreign gases increase with increasing dipole moment and polarizability of colliding molecules. In the temperature range 433–513 K, we obtained an inverse temperature dependence of the V–V-transfer efficiency, which is satisfactorily described by empirical relations taking into account long-range attractive forces. The results obtained point to the determining role of long-range attractive forces in quasi-resonance V–V-transfer of vibrational energy by molecules excited in vibrational quasi-continuum.

Three-dimensional nonperturbative analytic model of vibrational energy transfer in atom–molecule collisions

A three-dimensional semiclassical analytic model of vibrational energy transfer in collisions between a rotating diatomic molecule and an atom has been developed. The model is based on analysis of classical trajectories of a free-rotating (FR) molecule acted upon by a superposition of repulsive exponential atom-to-atom potentials. The energy transfer probabilities have been evaluated using the nonperturbative forced harmonic oscillator (FHO) model. The model predicts the probabilities for vibrational energy transfer as functions of the total collision energy, orientation of a molecule during a collision, its rotational energy, and impact parameter. The model predictions have been compared with the results of three-dimensional close-coupled semiclassical trajectory calculations using the same potential-energy surface. The comparison demonstrates not only remarkably good agreement between the analytic and numerical probabilities across a wide range of collision energies, but also shows that the analytic FHO-FR model correctly reproduces the probability dependence on other collision parameters such as rotation angle, angular momentum angle, rotational energy, impact parameter, and collision reduced mass. The model equally well predicts the cross sections of single-quantum and multiquantum transitions and is applicable up to very high-collision energies and quantum numbers. Most importantly, the resultant analytic expressions for the probabilities do not contain any arbitrary adjustable parameters commonly referred to as “steric factors.” The model provides new insight into kinetics of vibrational energy transfer and yields accurate expressions for energy-transfer rates that can be used in kinetic modeling calculations.

Vibrational relaxation and energy transfer in the hydrogen system at temperatures between 110 and 300 K

The collisional relaxation and vibrational energy transfer of vibrationally excited hydrogen H 2( v″=1) has been investigated in a low-pressure (5.33 hPa) Teflon-coated fast-flow (17 m s −1) reactor in the temperature range 110 K< T<300 K. Vibrationally excited hydrogen was produced through microwave discharges prior to mixing with helium or D 2. Relative concentration distributions of hydrogen species were monitored along the flow tube axis via Q-branch transitions using vibrational coherent anti-Stokes Raman spectroscopy (CARS). Wall deactivation probabilities and thermal rate constants for the vibrational energy transfer in collisions with D 2( v″=0) were determined as a function of temperature from a direct comparison of measured concentration profiles with results from computational modeling of the reactive flow using a numerical flow code with appropriate chemical kinetics. Results are compared with experiments and theoretical models from the literature.

The calculation of TV, VT, VV, VV' − rate coefficients for the collisions of the main atmospheric components

Abstract. The first-order perturbation approximation is applied to calculate the rate coefficients of vibrational energy transfer in collisions involving vibrationally excited molecules in the absence of non-adiabatic transitions. The factors of molecular attraction, oscillator frequency change, anharmonicity, 3-dimensionality and quasiclassical motion have been taken into account in the approximation. The analytical expressions presented have been normalized on experimental data of VT-relaxation times in N2 and O2 to obtain the steric factors and the extent of repulsive exchange potentials in collisions N2-N2 and O2-O2. The approach was applied to calculate the rate coefficients of vibrational-vibrational energy transfer in the collisions N2-N2, O2-O2 and N2-O2. It is shown that there is good agreement between our calculations and experimental data for all cases of energy transfer considered.Key words. Ionosphere (Auroral ionosphere; ion chemistry and composition). Atmospheric composition and structure (Aciglow and aurora).

Role of highly efficient collisions in collisional transfer of vibrational energy in benzophenone-foreign gas mixtures

Collisional losses of vibrational energy in mixtures of benzophenone excited by nitrogen laser radiation (λ=337 nm) and foreign gases (Ar, Kr, SF6, C5H12) were studied by time-resolved delayed luminescence. It is established that the intensities and rates of decay of the fast and slow components of delayed luminescence can be used to evaluate the characteristics of V–V– and V–T–transfer of vibrational energy. For the V-V-process, the efficiencies and mean energies transferred in a collision are determined. It is shown that in the mixture with multiatomic gases, vibrational equilibrium is reached after a few collisions, the number of which decreases as the molecule of the foreign gas becomes more complicated. The V–V–process is characterized by high efficiencies of collisions typical for “supercollisions”. The experimental characteristics of V-V-transfer correlate well with ergodic transfer of vibrational energy predicted by statistical theories. 0120 0126 V 3

Relaxation within and from the (31/214151) and (3141/214251) Fermi dyads in acetylene: Vibrational energy transfer in collisions with C2H2, N2 and H2

Infrared–ultraviolet double resonance (IRUVDR) experiments have been performed on samples of pure C2H2 and on C2H2 diluted in N2 and H2. Pulses of tunable IR radiation from an optical parametric oscillator (OPO) excited molecules of C2H2 to one component state of one of two Fermi dyads in the 1Σg+ electronic ground state, i.e. (31/214151)II or (3141/214251)II, and tunable UV laser radiation was used to observe the evolution of population either in that state or in the other component state of the same Fermi dyad. In this paper,‡ rate coefficients are reported for two kinds of processes: (a) vibration-to-vibration (V–V) transfer between the two component states of the same Fermi dyad induced by collisions with C2H2, N2 and H2, and (b) vibrational relaxation from the coupled pair of Fermi dyad states in collisions with the same gases. In addition, populations have been observed in the (4251), (4151) and (42) states of C2H2 during relaxation from the (3141/214251) dyad and rate coefficients for self-relaxation from the first two of these states have been derived. The results for both V–V intradyad transfer and for vibrational relaxation are discussed in terms of the vibrational matrix elements for such collision-induced transitions and differences in the mixing of the zero order states in the Fermi dyads.

Collisional energy transfer, intramolecular vibrational relaxation and unimolecular reactions

Experiments on (a) association reactions at very high pressures and (b) vibrational relaxation between species capable of forming a strong chemical bond have confirmed the hypothesis that, for the same chemical system, these two rates are essentially the same, both reflecting the rate of formation of collision complexes. The results of these measurements are reviewed. Subsequently, cases are discussed where the attraction between the collision partners is less strong. In these cases, it seems that the vibrational relaxation rate corresponds to a lower limit for complex formation, as complexes formed in collisions involving a vibrationally excited species may redissociate before intramolecular vibrational relaxation within the complex randomises the energy located in the initially excited vibration. A number of examples, CH+N2, NO+NO2, NO+NO, several ion–molecule systems and several involving OH and unsaturated molecules, where this behaviour seems to be occurring are discussed. It is emphasised that, whether or not the limiting, ‘strong attraction’, behaviour is observed will depend on the energy of the colliding species and therefore, in thermal experiments, on temperature. Finally, some consideration is given to the state-to-state aspects of vibrational energy transfer in collisions proceeding via collision complexes.

Collisional transfer of vibrational energy in vapors of polyatomic molecules

Thc collisional transfer of vibrational energy has been the subject of much investigation l 1, 2 ], the results of which are of fundamental importance for the molecular physics of the gas phase and have numerous practical applications. However, the laws governing intermolecular vibrational relaxation in the quasi-continuum of vibrational states, which is characteristic of polyalomic molecules even at comparatively low levcls of vibrational excitation, have not rcceived sufficient study. This results from the limited number of direct expcrimenlal methods and from the absence of corresponding theoretical models. Experimental difficulties are responsiblc for the differences in the quantitative characteristics of collisional transfer as well as ira the laws governing their variation with an increase in the internal energy of the molecule. The diversity of the postulated means of deactivation of excited molecules and the complexity' of the energy spectrum and of the motion dynamics of polyatomic molecules make simulation of the process difficult and require new, original experimental works along these lines. As early as in the late fifties, B. S. Neporent and N. A. Borisevich [3 I demonstrated lhe high cfficiencv of luminescence methods as applied to the study of collisional transfer of vibrational energy. A new direct method of obsem'ing the process of collisional transfer and exchange of vibrational energy from the change in the rates of decay of the delayed fluorescence activated by the nonequilibrium vibrational laser excitation of triplet molecules was suggested in I4 1. In subsequent works 15-71 il was shown that the use of multiphoion excitalion (MPE) of triplet molecules by CO2-taser radiation permits onc to investigate the process at both low and high vibrational energies for molecules of differcnl degrees of complexity. In the present work the method is used Io investigatc the energy dependences of the characteristics of the collisional transfer of vibrational energy ira vapors of diacclvl and benzophenone and their mixtures with foreign gases. As noted earlier, the choice of objects for investigalion is based on the spectroscopic charactcristics of the molecules, which in the gas phase possess long-lived triplcl states, a low barrier to the activation of delayed fluorescence, resulting from efficicnt Tl----" SI interconversion, and the ability to absorb thc IR radiation of a CO2-1aser in the electron ground and tripleT, states. The characteristics of the collisional transfer of vibrational energy are estimated using dcpendences of {he intensities and rates of decay Kdc c of the fast, microsecond component of activated fluorescence on the pressures of the vapors and foreign gases. The pressure dependence of Kde c varies in the investigated range of pressures and energies of excitation. At a constant density of CO2-1ascr energy, the rate of decay Kde c increases linearly with the pressures of the vapors and foreign gases only in a limited range of pressures and then begins to decrease. It should be noted that such dependences in mixtures with foreign gases are obscrvcd when there is a noticeable increase in the range of the values of ECO 2 used to the higher side. Anomalous dependences manifesting themselves in a decrease of Kde c with pressure begin to dominate at low laser energy densities. The dependences of the instantaneous values of lhe relative intensity l(v, 0/lo (v, t), where l(v, 0 and lo(v, t) are the intensities of luminescence at the maximum of the pulse of the activated fluorescence and of the

State-to-State Collisional Vibrational Energy Transfer in S1 p-Difluorobenzene

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTState-to-State Collisional Vibrational Energy Transfer in S1 p-DifluorobenzeneDavid L. Catlett Jr., Charles S. Parmenter, and Christopher J. PursellCite this: J. Phys. Chem. 1994, 98, 13, 3263–3269Publication Date (Print):March 1, 1994Publication History Published online1 May 2002Published inissue 1 March 1994https://doi.org/10.1021/j100064a003RIGHTS & PERMISSIONSArticle Views28Altmetric-Citations24LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (844 KB) Get e-Alerts

A BOXCARS investigation of vibrational relaxation in highly excited 1, 2-trans-dichloroethene

The BOXCARS technique has been used to study the collisional vibrational energy transfer from 1, 2-trans-dichloroethene excited into a quasicontinuum by a pulsed CO2 laser. The temporal evolution behaviour for vibrational energies in different modes was obtained. It has been shown that both the rate and maximum energy transferral to the ν4 mode are slightly larger than rates and energy transferral to the ν1 and ν2 modes and that this specificity declines with increase in excitation energy. The mechanism for this specificity is discussed.

Collisional energy transfer in predissociative OH laser-induced fluorescence in flames

Collisional vibrational energy transfer from the predissociative v′ = 3 level of the OH A ∑+ state was studied with laser-induced fluorescence. For CH4/O2, CH4/air, and H2 /O2 flames at pressures ranging from 14 to 760Torr, the v′= 3 level was excited, and transfer into the lower v′ = 0, 1, 2 levels was measured. Energy transfer occurred in all flames, as exemplified by the 760-Torr CH4 /air flame in which only 30% of the total ultraviolet fluorescence emitted came from the initially excited v′ = 3 level. For quantitative measurements, one must either correct for vibrational energy transfer or alter the detection strategy to collect only fluorescence emitted by v′ = 3

Collisional vibrational relaxation of a triplet state: Energy-dependent energy loss from T1 pyrazine

The loss of vibrational energy from gas phase T1 pyrazine molecules has been measured for thermal collisions with helium, argon, H2, SF6, and ground state pyrazine. Triplet pyrazine was prepared with a well defined vibrational energy of 5433 cm−1 through S1→T1 intersystem crossing following optical excitation to the 8a1 level of S1. The time-dependent vibrational energy content of the excited pyrazine molecules was then deduced using a recently developed ‘‘direct’’ method involving the kinetics of subsequent T1→S0 intersystem crossing. For each of the collision partners studied, it was possible to find the average energy lost per gas kinetic collision for donor energies ranging from ca. 2000 to 5433 cm−1. The magnitudes of these energy losses generally increased with the mass and vibrational complexity of the relaxing collision partner. For vibrational energy contents near 5000 cm−1, relaxation of the triplet pyrazine was enhanced by factors of as much as 24 relative to S0 benzene at a similar vibrational energy. In addition, with all collision partners studied the average energy lost per collision showed appparent threshold behavior near 3000 cm−1, increasing by approximately an order of magnitude as the donor’s energy increased from 2500 to 5000 cm−1. The findings of this first quantitative study of triplet relaxation suggest that collisional vibrational energy transfer from organic triplet states may proceed by mechanisms different from those that dominate ground state relaxation.