Observation of predicted resonance structure in the H+D2 --> HD(v(') = 0, j(') = 7) + D reaction at a collision energy of 0.94 eV

We present experimental verification of predicted resonance structure in the energy dependence of the H+D2 reaction. Specifically we predict and observe a broad resonance in the H+D2-->HD(v(') = 0,j(') = 7)+D reaction at a collision energy of 0. 94 eV. This resonance structure is roughly Gaussian with a full width at half maximum of 0.1 eV. These results represent the first experimentally observed resonance structure in the fundamental H+H2 reaction system.     

Resonances and chaos in the collinear collision system (He,H 2 + ) and its isotopic variants

The collinear atom-diatom collision system provides one of the simplest instances of chaotic or irregular scattering. Classically, irregular scattering is manifest in the sensitive dependence of post-collision variables on initial conditions, and quantally, in the appearance of a dense spectrum of dynamical resonances. We examine the influence of kinematic factors on such dynamical resonances in collinear (He, H ₂ ⁺ ) collisions by computing the transition state spectra for collinear (He, HD⁺) and (He, DH⁺) collisions using the time-dependent quantum mechanical approach. The nearest neighbor spacing distributionP(s) and the spectral rigidity Δ₃(L) for these resonances suggest that the dynamics is predominantlyirregular for collinear (He, HD⁺) and predominantlyregular for collinear (He, DH⁺). These findings are reinforced by a significantly larger “correlation hole” in ensemble averaged survival probability ≪P(t)≫ values for collinear (He, HD⁺) than for collinear (He,DH⁺). In addition we have also examined measures of classical chaos through the dependence of the final vibrational action,n _f, on the initial vibrational phaseφ _i of the diatom, and Poincaré surfaces-of-section. They show that (He, HD⁺) collisions are partly chaotic over the entire energy range (0–2.78 eV) while (He, DH⁺) collisions, in contrast, are highly regular at collision energies below the classical threshold for reaction. Above the threshold, the scattering remains regular for initial vibrational statesv=0 and 1 of DH⁺.     

Experimental and quantum dynamical study on an asymmetric insertion reaction: state-to-state dynamics of O(1D) + HD(1Sigmag+, v' = 0, j' = 0)-->OH(Pi, v", N") + D(2S)

Quantum-state-resolved differential cross sections of the O((1)D) + HD --> OH + D reaction at the collision energy of 7.11 kJ/mol has been determined experimentally and theoretically. The results of the time-dependent wave-packet calculations are overall in good agreement with the crossed beam scattering data, providing a benchmark example of an asymmetric insertion reaction at the state-to-state scattering level. The good agreement between experiment and theory suggests that the underlying ground potential energy surface is generally correct and that the nonadiabatic effect involving the electronic excited pathway is apparently small in this system.     

Theoretical study of stereodynamics for the reaction O(3P) +D2 (v=0, j=0) to OD+D and isotope effect

Quasi-classical trajectory (QCT) calculations have been performed to study the product polarization behaviours in the reaction O(³P) + D₂ (v= 0, j= 0)→OD + D. By running trajectories on the ³A′ and ³A″ potential energy surfaces (PESs), vector correlations such as the distributions of the polarization-dependent differential cross sections (PDDCSs), the angular distributions of P(θ_r) and P(ø_r) are presented. Isotope effect is discussed in this work by a comprehensive comparison with the reaction O(³P) + H₂ (v= 0, j= 0) → H + H. Common characteristics as well as differences are discussed in product alignment and orientation for the two reactions. The isotope mass effect differs on the two potential energy surfaces: the isotope mass effect has stronger influence on P(θ_r) and PDDCSs of the ³A′ PES while the opposite on P(ø_r) of the ³A″ potential energy surface.     

Ionisation energy values for the vibronic transitions from HCl X1 Σ+ (v″ = 0) to HCl+ ionic states X2 Π (v′ = 0

High-resolution Ne (I) (73.6 nm) photoelectron spectroscopic measurements provide values of the ionisation energies to the first 14 vibrational levels     

Analysis of the (0 0 v(3)), v(3) = 1, 2, 3 Vibrotational States of HDSe

High-resolution Fourier transform spectra of HDSe in the region of the 2nu(3) and 3nu(3) bands were recorded and analyzed for five different (M)Se isotopic HDSe species. Energies obtained from rovibrational analyses of the (002) and (003) states, together with those taken of the (001) state from an earlier study [O. N. Ulenov, G. A. Onopenko, N. E. Tyabaeva, H. Bürger, and W. Jerzembeck, J. Mol. Spectrosc. 198, 27-39 (1999)], were used as input information for a "Global Fit" procedure. This fit provided 34 spectroscopic parameters for the HD(80)Se species which reproduced rotational-vibrational transitions of the (001), (002), and (003) states within experimental accuracy. Corresponding analyses were performed for the other (M)Se (M = 82, 78, 77, and 76) species. Copyright 2000 Academic Press.     

Theoretical study on collision dynamics of H+ + H2O at low energies

Scattering dynamics of a water molecule in collision with proton is studied based on a time-dependent density functional theory and coupled with the molecular dynamics method, in which the electrons are described by quantum mechanics and the nuclei are described by classical mechanics. Four different incident directions at 46 eV are chosen in order to investigate the orientations effect, and the energy-dependent effect in low energy region is explored under impact energies 27, 36 and 46 eV. Reaction channels, scattering angles and energy loss of protons are calculated. The differences between those characteristics are unobvious in large impact parameters, which are irrespective of the incident orientations due to weak projectile-target interaction. In small impact parameters, the results strongly depend on the collision energy and orientation.     

Theoretical study and rate constant calculation for the O(3P) + C2H5CN reaction

The complicated microscopic reaction mechanisms of O(³P) with C₂H₅CN on the ground electronic state energy surface have been investigated at the G3(MP2) level of theory based on the geometric parameters optimized at the B3LYP/6-311 + G(d, p) level. Two kinds of H-abstraction and addition–elimination channels are considered, namely methylene-H abstraction, methyl-H abstraction, C-addition/elimination and N-addition/elimination. The kinetics of the title reaction have been studied using the TST and multichannel RRKM methodologies over a wide temperature range of 200–2000 K. The results show that the methylene-H abstraction process is predominant for the whole reaction. With an increase of temperature, H-abstraction from the methyl position channel should be taken into account. The C-addition/elimination process provides a few contributions to the title reaction compared with two kinds of H-abstraction channels over the whole temperature region and the N-addition/elimination channel can be negligible due to the high entrance barrier and unstable products.     

Dynamics of the reaction of O with H2 and its isotopic variants in different rotational excited states

Scalar properties and vector correlations of the reactions of O+H 2 →OH+H, O+HD→OH+D, O+DH→OD+H, and O+D 2 →OD+D at collision energies of 25 and 34.6 kcal/mole have been studied via the quasi-classical-trajectory (QCT) method based on a BMS1 potential energy surface (PES). The generalized polarization-dependent differential cross section and the distributions of the dihedral angle at the collision energy of 34.6 kacl/mole are presented. The calculated results indicate that both the reagent rotational angular momentum and the mass factor have a significant influence on the scalar properties and vector correlations of the title reactions.     

On the features of statistical behaviour of the O(<Superscript>3</Superscript>P)+HCl(v = 2, j = 1,6,9) → OH + Cl reaction

The O(³P)+HCl(v = 2, j = 1,2,6) → OH+Cl reaction has been theoretically studied by means of a statistical quantum model and an exact time independent method. Although the statistical method is based on the assumption of a complex-forming mechanism, which seems not be the case for this process, the OH(v' = 1) product channel, specially when the HCl reagent is rotationally excited to j = 1, exhibits features of statistical behaviour. In fact, experimental rotational distributions and previous exact quantum mechanical integral cross sections are well described by present statistical results. A possible explanation for this feature is given in terms of the existence of a dynamical well which strongly correlates the initial (v = 2, j = 1) state with the v'=1 final manifold. The method is not capable though to account for the vibrational inversion seen for this process and results obtained for the vibrationless OH formation are in clear disagreement with previous findings.     

High-Resolution Fourier Transform Emission Spectroscopy of the B(2)Sigma(+) (v = 0)-X(2)Sigma(+) (v = 0) Transition of the PN(+) Ion

Ultraviolet emission spectrum of the B(2)Sigma(+) (v = 0)-X(2)Sigma(+) (v = 0) transition of the PN(+) ion has been observed at a resolution of 0.05 cm(-1) by a Fourier transform spectrometer. The rotational analysis led to a great improvement of rotational constants in the B(2)Sigma(+) (v = 0) and X(2)Sigma(+) (v = 0) states as well as to the first determination of centrifugal distortion constants for both levels and spin-rotation interaction constant in the X(2)Sigma(+) (v = 0) state. Rotational perturbation in the B(2)Sigma(+) (v = 0) state was observed. Copyright 2000 Academic Press.     

Electron screening in the 1H(7Li,$ alpha$)4He reaction

We have measured the cross-section for the ¹H(⁷Li,a alpha)⁴He reaction at lithium beam energies from 0.34 to 1.05MeV. Hydrogen was forced by diffusion into Pd and PdAg alloy foils. A large electron screening effect was observed only when foils were under tensile stress. A dependence of the screening potential on hydrogen concentration or Hall coefficient of the metallic host could not be established.     

High-Resolution Fourier Transform Spectra of HDSe: The Interacting States (v(1) v(2) v(3))/(v(1) +/- 1 v(2) -/+ 2 v(3)) with 2v(1) + v(2) = 1, 2, 3, and 4

For the first time, high-resolution Fourier transform spectra of HDSe in the region of the three polyads, nu(1)/2nu(2), nu(1) + nu(2)/3nu(2), and 2nu(1)/nu(1) + 2nu(2)/nu(2) + nu(3), have been recorded and analyzed. Combined with an earlier investigation of the nu(2) band, and including estimates for the unobserved "dark" 4nu(2) band, these levels were subjected to a "Global Fit," which makes use of relations between parameters within the different polyads. Since there are five isotopic species present in natural HD(M)Se (M = 82, 80, 78, 77, 76), altogether 34 vibration-rotation bands have been studied in the present contribution. The parameters determined by the Global Fit reproduce upper vibrational-rotational energies of all these bands with accuracies close to experimental precision. Copyright 2000 Academic Press.     

High-resolution study of 0+ and 2+ excitations in 168Er with the (p, t) reaction

Excited states in the deformed nucleus ¹⁶⁸Er have been studied with high energy resolution in the (p, t) reaction, with the Munich Q3D spectrograph. A large number of excited 0⁺ states (25) and 2⁺ states (64) have been assigned up to 4.0-MeV excitation energy. This allows detailed investigations along two directions of current interest: first, an extension of microscopic model interpretations into the region of medium level density above the pairing gap; second, a first analysis of the statistical fluctuation (order/chaos) properties of pure sequences of levels, in one deformed nucleus. Predictions of two models (the quasiparticle-phonon model and the projected shell model) are compared to the data, and it is concluded that, in both cases, mixing of more configurations is required in the wave functions. The text was submitted by the authors in English.