On the dynamics of the H[sup +]+Dsub 2→HD+D[sup +] reaction: A comparison between theory and experiment (original) (raw)
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On the dynamics of the H++D2(v=0,j=0)→HD+D+ reaction: A comparison between theory and experiment
Journal of Chemical Physics, 2008
The H + +D 2 ͑v =0, j =0͒ → HD+D + reaction has been theoretically investigated by means of a time independent exact quantum mechanical approach, a quantum wave packet calculation within an adiabatic centrifugal sudden approximation, a statistical quantum model, and a quasiclassical trajectory calculation. Besides reaction probabilities as a function of collision energy at different values of the total angular momentum, J, special emphasis has been made at two specific collision energies, 0.1 and 0.524 eV. The occurrence of distinctive dynamical behavior at these two energies is analyzed in some detail. An extensive comparison with previous experimental measurements on the Rydberg H atom with D 2 molecules has been carried out at the higher collision energy. In particular, the present theoretical results have been employed to perform simulations of the experimental kinetic energy spectra.
The Journal of Chemical Physics, 2005
The H(+)+D(2) and D(+)+H(2) reactive collisions are studied using a recently proposed adiabatic potential energy surface of spectroscopic accuracy. The dynamics is studied using an exact wave packet method on the adiabatic surface at energies below the curve crossing occurring at approximately 1.5 eV above the threshold. It is found that the reaction is very well described by a statistical quantum method for a zero total angular momentum (J) as compared with the exact ones, while for higher J some discrepancies are found. For J >0 different centrifugal sudden approximations are proposed and compared with the exact and statistical quantum treatments. The usual centrifugal sudden approach fails by considering too high reaction barriers and too low reaction probabilities. A new statistically modified centrifugal sudden approach is considered which corrects these two failures to a rather good extent. It is also found that an adiabatic approximation for the helicities provides results in very good agreement with the statistical method, placing the reaction barrier properly. However, both statistical and adiabatic centrifugal treatments overestimate the reaction probabilities. The reaction cross sections thus obtained with the new approaches are in rather good agreement with the exact results. In spite of these deficiencies, the quantum statistical method is well adapted for describing the insertion dynamics, and it is then used to evaluate the differential cross sections.
The Journal of Chemical Physics, 2006
The H + +H 2 exchange reaction has been studied theoretically by means of a different variety of methods as an exact time independent quantum mechanical, approximate quantum wave packet, statistical quantum, and quasiclassical trajectory approaches. Total and state-to-state reaction probabilities in terms of the collision energy for different values of the total angular momentum obtained with these methods are compared. The dynamics of the reaction is extensively studied at the collision energy of E coll = 0.44 eV. Integral and differential cross sections and opacity functions at this collision energy have been calculated. In particular, the fairly good description of the exact quantum results provided by the statistical quantum method suggests that the dynamics of the process is governed by an insertion mechanism with the formation of a long-lived collision complex.
The Journal of Chemical Physics, 2004
An experimental and theoretical investigation of the collision energy dependence of the HD(Ј ϭ2,jЈ) rotational product state distribution for the HϩD 2 reaction in the collision energy range of E col ϭ1.30-1.89 eV has been carried out. Theoretical results based on time-dependent and time-independent quantum mechanical methods agree nearly perfectly with each other, and the agreement with the experiment is good at low collision energies and very good at high collision energies. This behavior is in marked contrast to a previous report on the HD(Јϭ3,jЈ) product state rotational distribution ͓Pomerantz et al., J. Chem. Phys. 120, 3244 ͑2004͔͒ where a systematic difference between experiment and theory was observed, especially at the highest collision energies. The reason for this different behavior is not yet understood. In addition, this study employs Doppler-free spectroscopy to resolve an ambiguity in the E, F -X resonantly enhanced multiphoton ionization transition originating from the HD(Јϭ2,jЈϭ1) state, which is found to be caused by an accidental blending with the transition coming from the HD(Јϭ1,jЈϭ14) state.
The Journal of Chemical Physics, 2005
Product rotational distributions for the reaction H + D 2 → HD͑Ј =1, jЈ͒ + D have been measured for 16 collision energies in the range of 1.43ഛ E coll ഛ 2.55 eV. Time-dependent quantum-mechanical calculations agree well in general with the experimental results, but they consistently yield slightly colder distributions. In terms of the average energy channeled into rotation, the differences between experiment and theory amount to approximately 10% for all collision energies sampled. No peculiarity is found for E coll = 2.55 eV at which the system has sufficient energy to access the first HD 2 electronically excited state.
The Journal of Chemical Physics, 1984
Two-photon resonance, three-photon ionization has been used to determine the HD product internal state distribution formed by the reaction of fast H atoms with thermal D2 molecules. A mixture of HI and D2 is irradiated by a 266 nm laser pulse to dissociate the former, giving a centerof-mass collision energy of about 1.30 ± 0.04 eV for H + D 2 . After a sufficiently short delay to ensure essentially collision-free conditions, a second laser is fired which causes multiphoton ionization of individual HD quantum states as well as D atoms, depending upon the choice of wavelength. Reaction occurs in a well-defined effusive flow which emerges from a glass orifice placed between the acceleration plates of a differentially pumped time-of-flight mass spectrometer. Ion signals are referenced to those obtained from HD or D produced in an auxiliary microwave discharge. Relative formation rates are reported for HD(v = 1, J = 0--6) and HD(v = 2, J = 0--6). Nascent D atoms are also observed and an upper limit is placed on the production ofHD(v = 3). Rotational surprisal plots are found to be linear for the HD product state distribution yielding a slope ofe R = 5.1 for HD(v = 1) and e R = 4.7 for HD(v = 2). These are extrapolated to provide full distributions for HD(v = 0--2, J = 0--6). The present product state distributions are compared with the recent experimental data of Gerrity and Valentini as well as with the quasiclassical trajectory calculations of Blais and Truhlar.
The D+H2(v=1,j)→HD(v’,j’)+H reaction. A detailed quasiclassical trajectory study
The Journal of Chemical Physics, 1994
Thorough quasiclassical trajec;tory (QCT) calculations have been carried out for the D+H 2 (v = l,j) exchange reaction. These calculations include integral and differential cross sections, rate constants, reaction probabilities as a function _of total energy, opacity functions, and distributions of internal states of the HD product in the range of collision energies from the reaction threshold to 1.5 eV and initial j values from 0 to 12. An overall good agreement with some discrepancies is found between the present QCT results and those from experiments and accurate quantum-mechanical calculations.
The Journal of Chemical Physics, 2012
In this work we critically revise several aspects of previous ab initio quantum chemistry studies [P. Palmieri et al., Mol. Phys. 98, 1835; C. N. Ramachandran et al., Chem. Phys. Lett. 469, 26 (2009)] of the HeH + 2 system. New diatomic curves for the H + 2 and HeH + molecular ions, which provide vibrational frequencies at a near spectroscopic level of accuracy, have been generated to test the quality of the diatomic terms employed in the previous analytical fittings. The reliability of the global potential energy surfaces has also been tested performing benchmark quantum scattering calculations within the time-independent approach in an extended interval of energies. In particular, the total integral cross sections have been calculated in the total collision energy range 0.955-2.400 eV for the scattering of the He atom by the ortho-and para-hydrogen molecular ion. The energy profiles of the total integral cross sections for selected vibro-rotational states of H + 2 (v = 0, . . . ,5 and j = 1, . . . ,7) show a strong rotational enhancement for the lower vibrational states which becomes weaker as the vibrational quantum number increases. Comparison with several available experimental data is presented and discussed.
The Journal of Chemical Physics, 1994
A detailed comparison of quasiclassical trajectory (QCT) and quantum mechanical (QM) reaction probabilities and differential cross sections for the H + D 2-+ HD + D reaction at the collision energies of 0.54 and 1.29 e V has been carried out using the same potential energy surface. The theoretical simulation of the recently published experimental results is also reported. The comparisons made here demonstrate the level of agreement between QCT and QM approaches, as well as between theory and experiment for this reaction.