Scattering of Stark-decelerated OH radicals with rare-gas atoms

We present a combined experimental and theoretical study on the rotationally inelastic scattering of OH (X\,^2\Pi_{3/2}, J=3/2, f) radicals with the collision partners He, Ne, Ar, Kr, Xe, and D$_2$ as a function of the collision energy between $\sim 70$ cm$^{-1}$ and 400~cm$^{-1}$. The OH radicals are state selected and velocity tuned prior to the collision using a Stark decelerator, and field-free parity-resolved state-to-state inelastic relative scattering cross sections are measured in a crossed molecular beam configuration. For all OH-rare gas atom systems excellent agreement is obtained with the cross sections predicted by close-coupling scattering calculations based on accurate \emph{ab initio} potential energy surfaces. This series of experiments complements recent studies on the scattering of OH radicals with Xe [Gilijamse \emph{et al.}, Science {\bf 313}, 1617 (2006)], Ar [Scharfenberg \emph{et al.}, Phys. Chem. Chem. Phys. {\bf 12}, 10660 (2010)], He, and D$_2$ [Kirste \emph{et al.}, Phys. Rev. A {\bf 82}, 042717 (2010)]. A comparison of the relative scattering cross sections for this set of collision partners reveals interesting trends in the scattering behavior.Comment: 10 pages, 5 figure

LASER INDUCED FLUORESCENCE SPECTROSCOPY OF THE C4HC_{4}H AND C4DC_{4}D RADICALS

$^{a}$C. A. Gottlieb, E. W. Gottlieb, P. Thaddeus, and M. Kawamura, Astrophys. J. 275, 916 (1983). $^{b}$D. R. Woodward, J. C. Person, C. A. Gottlieb,and C. A. Thaddeus, Astrophys. J. 333, L29 (1988). $^{c}$A. L. Sobolewski and L. Adamowicz, J. Chem. Phys. 102, 394 (1995).Author Institution: Department of Pure and Applied Sciences, College of Arts and Sciences, The University of Tokyo; Department of Chemistry, Graduate School of Science, Kyoto UniversityLaser-induced-fluorescence spectra of the $C_{4}H$ and $C_{4}D$ radicals have been observed for the first time. The molecules were generated in a supersonic jet by an electric discharge of $C_{2}H_{2}$ or $C_{2}D_{2}$ diluted in Ar. Fourteen and thirteen vibronic bands were observed for $C_{4}H$ and $C_{4}D$ respectively, in the near UV region (24000 - 25000 $cm^{-1}$). The bands were assigned to the $^{2}\Sigma-^{2}\Sigma$ or $^{2}\Pi-^{2}\Sigma$ type and several $^{2}\Sigma-^{2}\Sigma$ bands were subjected to rotational analyses. The determined rotational constants for the lower state agree with those for $C_{4}H/C_{4}D$ in the ground vibrational level in the $X^{2}\Sigma$ state, which were reported in a previous microwave study $^{a,b}$. The spin-orbit splittings in the $^{2}\Pi-^{2}\Sigma$ bands are 16 and $12 cm^{-1}$ for $C_{4}H$ and $C_{4}D$, respectively, leading a conclusion that the excited electronic state for the observed band system is $^\Pi$. The present observation is consistent with a recent CASSCF $study^{c}$, which predicted the $B^{2}\Pi$ state with the excitation energy of $24500 cm^{-1}$

Pure Rotational Spectrum of CCl+

The pure rotational spectrum of the CCl+ (X-1 sigma(+)) cation has been observed for the first time using a cryogenic ion trap apparatus and applying an action spectroscopy scheme. The major isotopic species (CCl+)-C-12-Cl-35 was observed up to the J = 4 <- 3 transition around 191 GHz and (CCl+)-C-12-Cl-37 was observed up to J = 3 <- 2. All transitions exhibit (partially) resolved hyperfine structure from the presence of the chlorine nuclei (both I = 3/2). This study provides the data needed for future sensitive radio astronomical searches for CCl+ in space

Frequency-domain interferometry for the determination of time delay between two extreme-ultraviolet wave packets generated by a tandem undulator

Abstract Synchrotron radiation, emitted by relativistic electrons traveling in a magnetic field, has poor temporal coherence. However, recent research has proved that time-domain interferometry experiments, which were thought to be enabled by only lasers of excellent temporal coherence, can be implemented with synchrotron radiation using a tandem undulator. The radiation generated by the tandem undulator comprises pairs of light wave packets, and the longitudinal coherence within a light wave packet pair is used to achieve time-domain interferometry. The time delay between two light wave packets, formed by a chicane for the electron trajectory, can be adjusted in the femtosecond range by a standard synchrotron technology. In this study, we show that frequency-domain spectra of the tandem undulator radiation exhibit fringe structures from which the time delay between a light wave packet pair can be determined with accuracy on the order of attoseconds. The feasibility and limitations of the frequency-domain interferometric determination of the time delay are examined

Quantum-state resolved bimolecular collisions of velocity-controlled oh with no radicals

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Quantum mechanical calculation of energy dependence of OCl/OH product branching ratio and product quantum state distributions for the O(D-1) plus HCl reaction on all three contributing electronic state potential energy surfaces

OCl/OH product branching ratios are calculated as a function of total energy for the O(1D) + HCl reaction using quantum wavepacket methods. The calculations take account of reaction on all the three electronic state potential energy surfaces which correlate with both reactants and products. Our results show that reaction on the excited electronic state surfaces has a large effect on the branching ratio at higher energies and that these surfaces must therefore be fully taken into account. The calculations use the potential energy surfaces of Nanbu and co-workers. Product vibrational and rotational quantum state distributions are also calculated as a function of energy for both product channels. Inclusion of the excited electronic state potential energy surfaces improves the agreement of the predicted product vibrational quantum state distributions with experiment for the OH product channel. For OCl agreement between theory and experiment is retained for the vibrational quantum state distributions when the excited electronic state potential energy surfaces are included in the analysis. For the rotational state distributions good agreement between theory and experiment is maintained for energies at which experimental results are available. At higher energies, above 0.7 eV of total energy, the OCl rotational state distributions predicted using all three electronic state potential energy surfaces shift to markedly smaller rotational quantum numbers

Directional Control of Radiation Heat Transfer by V-Groove Cavities-Collimation of Energy in Direction Normal to Cavity Opening

for the case of p 0 = 0. The rays striking the emitter surface may cause the temperature increase, and may damage the heater surface. The heater is not damaged for the involute reflector because the emitted rays are not absorbed by the emitter. Comparison With Experimental Data. The experimental data for involute and circular arc reflectors show relatively good accordance. Especially the values in the vicinity of the aperture edges of IR agreed; nevertheless, the directional reflectivity of the aluminum was derived from the theoretical value for X = 0.5 ^m. In the experimental data, there are several parts that are smaller than the theoretical prediction. This is due to the fact that the directional radiant intensity on the surface of the fluorescent lamp is not ideally uniform, but is of a smaller value at large emission angle 9; hence, the effect results in a lower value of experimental data than the prediction. For practical application of the involute reflector, some deformation of the involute may be needed for improving the effect of unisotropic emission characteristics of the emitter surface