Collision energy dependence of the HD(nu'=2) product rotational distribution of the H+D2 reaction in the range 1.30-1.89 eV (original) (raw)
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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.
Journal of Chemical …, 2004
We present experimental rotational distributions for the reaction HϩD 2 →HD(Јϭ3,jЈ)ϩD at eight different collision energies between 1.49 and 1.85 eV. We combine a previous measurement of the state-resolved excitation function for this reaction ͓Ayers et al., J. Chem. Phys. 119, 4662 ͑2003͔͒ with the current data to produce a map of the relative reactive cross section as a function of both collision energy and rotational quantum number ͑an E-jЈ plot͒. To compare with the experimental data, we also present E-jЈ plots resulting from both time-dependent and time-independent quantum mechanical calculations carried out on the BKMP2 surface. The two calculations agree well with each other, but they produce rotational distributions significantly colder than the experiment, with the difference being more pronounced at higher collision energies. Disagreement between theory and experiment might be regarded as surprising considering the simplicity of this system; potential causes of this discrepancy are discussed.
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 Journal of Chemical Physics, 2004
We present experimental rotational distributions for the reaction HϩD 2 →HD(Јϭ3,jЈ)ϩD at eight different collision energies between 1.49 and 1.85 eV. We combine a previous measurement of the state-resolved excitation function for this reaction ͓Ayers et al., J. Chem. Phys. 119, 4662 ͑2003͔͒ with the current data to produce a map of the relative reactive cross section as a function of both collision energy and rotational quantum number ͑an E -jЈ plot͒. To compare with the experimental data, we also present E -jЈ plots resulting from both time-dependent and time-independent quantum mechanical calculations carried out on the BKMP2 surface. The two calculations agree well with each other, but they produce rotational distributions significantly colder than the experiment, with the difference being more pronounced at higher collision energies. Disagreement between theory and experiment might be regarded as surprising considering the simplicity of this system; potential causes of this discrepancy are discussed.
AIP Advances, 2012
The Diep and Johnson (DJ) H 2 -H 2 potential energy surface (PES) obtained from the first principles [P. Diep, K. Johnson, J. Chem. Phys. 113, 3480 (2000); 114, 222 (2000)], has been adjusted through appropriate rotation of the three-dimensional coordinate system and applied to low-temperature (T < 300 K) HD+o-/p-H 2 collisions of astrophysical interest. A non-reactive quantum mechanical close-coupling method is used to carry out the computation for the total rotational state-to-state cross sections σ j1j2→j ′ 1 j ′ 2 (ǫ) and corresponding thermal rate coefficients k j1j2→j ′ 1 j ′ 2 (T ). A rather satisfactory agreement has been obtained between our results computed with the modified DJ PES and with the newer H 4
Chemical Physics Letters, 1993
The reaction H+Da+HD(u'= 1, j') t D was studied using two different experimental geometries: (1) a probe-laser-induced reaction geometry and (2) an independent-photolysis laser geometry. High-energy H atoms were generated by photolysis of HI which resulted in center-of-mass collision energies of 2.2 and 2.5 eV for geometries 1 and 2, respectively. The HD product was detected using (2 t 1) REMPI and time-of-flight mass spectrometry. The HD(u'= 1, j') rotational distributions are presented; at this time no corresponding theoretical calculations are available for comparison.
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, 2001
We investigate the sensitivity of photoinitiated experiments to forward-scattering features by direct comparison of experimental angular distributions with quantum-mechanical calculations as well as by forward-convolution of theoretical and model center-of-mass differential cross sections. We find that the experimental sensitivity to forward-scattering angles depends on the instrumental velocity resolution as well as on the kinematics of the detected product channel. Explicit comparison is made between experimental HD(vЈϭ1,2; jЈ) center-of-mass angular distributions at collision energies Ϸ1.6 eV ͑deduced from time-of-flight profiles using a single-laser, photolysis-probe approach͒ and quantum-mechanical calculations on the BKMP2 potential energy surface. The comparison takes into account the contributions from both slow and fast H atoms from the photolysis of HBr. We find that the contribution of the slow H atoms, which is the major source of experimental uncertainty, does not greatly affect the extraction of the angular distribution from the experimental time-of-flight profile for a specific HD(vЈ, jЈ) state. Except for HD(vЈϭ1, jЈϭ8) and HD(vЈϭ2, jЈϭ0), for which either slow H atoms or the presence of a narrow forward-scattering peak make the analysis more uncertain, the agreement between experiment and theoretical predictions is excellent.