Search

The S(1D)+D2→SD+D reaction has been studied through a photolysis-probe experiment in a cell. S(1D) reagent was prepared by 193 nm photolysis of CS2, and the SD(X 2Π) product was detected by laser fluorescence excitation. The nascent rotational/fine-structure state distribution of the SD(X 2Π) product was determined. This reaction, previously studied theoretically and in a crossed molecular beam experiment, is known to proceed through formation and decay of a long-lived collision complex involving the deep well in the H2S ground electronic state. The determined SD rotational state distribution in the v=0 vibrational level was found to be approximately statistical, with a small preference for formation of the F1 (Ω=3/2) fine-structure manifold over F2 (Ω=1/2). The branching into the Λ doublet levels was also investigated, and essentially equal populations of levels of A′ and A″ symmetry were found. The present results are compared with previous investigations of this reaction and the analogous O(1D)+D2 reaction. © 2005 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Phase lag spectroscopic measurements are performed for HI and DI in the 5d(π, δ) resonance region. Measurements of the phase lags for both molecules reveals a strong isotopic effect, especially pronounced in the ionization channel. The energy dependence of the phase lag provides clear examples of continuum and resonance coupling effects that were previously predicted theoretically but have not yet been observed. It is demonstrated that phase lag spectroscopy is a sensitive technique for studying properties of molecular continua, furnishing information that is not available from phase-insensitive observables. [ABSTRACT FROM AUTHOR]

Carrier lifetime control in thick silicon carbide (SiC) epilayers is essential for fabricating >10kV devices. Lifetime depth profiles were investigated in n-type and p-type SiC epilayers using photoluminescence (PL) decay excited by two-photon absorption (TPA), using 586nm laser pulses. TPA limits the excitation to a small volume, and the observed PL decays exhibit nonexponential behavior resulting from the three-dimensional carrier diffusion occurring during the decay. The results were analyzed using a formalism that includes the effects of carrier lifetime, carrier diffusion, and surface recombination on the PL decay. The lifetime depth profiles exhibited a nonuniform lifetimedegrading defect concentration within the epilayers. [ABSTRACT FROM AUTHOR]

In the discharge of oscillating electrons, the mechanism of the processes, which controls the distribution of the ion and electron streams over the cathode surface, is investigated experimentally. The influence of the length of the discharge interval on value and distribution of the ion and electron streams is analyzed. The distribution both of ion and electron streams at the cathode surface is determined at different conditions of the discharge. It is shown that for given values of the anode diameter da=31 mm and the gas pressure P=5×10-5 Torr, the intensive stream of positive ions falls entirely on the cathode central area in the whole interval of the anode length variation (ℓa=1–11 cm). At the cathode, the ion current reaches the maximal value at a certain (optimal) value of the anode length that, in turn, depends on the anode voltage Ua. The intensive stream of longitudinal electrons forms in the short anodes only (ℓa=2.5–3.5 cm) and depending on the choice of the discharge regime, may fall both on central and middle parts of the cathode. [ABSTRACT FROM AUTHOR]

We report temperature-dependent measurements of the terahertz (THz) vibrational spectrum of ammonium nitrate (AN) films and mixed potassium nitrate (KN)-ammonium nitrate films using waveguide THz time domain spectroscopy. The experiments were performed on polycrystalline films on the metal surface of a parallel plate waveguide. At cryogenic temperature and with frequency resolution as high as 7 GHz, our measurements produce a complex vibrational spectrum for AN, and show vibrational resonances not observed in previous far infrared and Raman measurements. We investigate potential interactions between AN and the metal surface by measuring THz spectra of films on aluminum, gold, and a gold surface coated with an organic self-assembled monolayer. Measurements are also performed on a deuterated AN film and indicate that the observed THz modes are due largely to the motion of the nitrate ions in the AN crystal. Finally, the effect of introducing small amounts of an impurity into the AN lattice is examined. We find that introduction of as little as 1%-2% by weight of potassium nitrate into the AN lattice causes line broadening of the THz modes, which is consistent with increased disorder introduced by the impurity. [ABSTRACT FROM AUTHOR]

The S(1D)+D2-->SD+D reaction has been studied through a photolysis-probe experiment in a cell. S(1D) reagent was prepared by 193 nm photolysis of CS2, and the SD(X 2Pi) product was detected by laser fluorescence excitation. The nascent rotational/fine-structure state distribution of the SD(X 2Pi) product was determined. This reaction, previously studied theoretically and in a crossed molecular beam experiment, is known to proceed through formation and decay of a long-lived collision complex involving the deep well in the H2S ground electronic state. The determined SD rotational state distribution in the v=0 vibrational level was found to be approximately statistical, with a small preference for formation of the F1 (Omega=3/2) fine-structure manifold over F2 (Omega=1/2). The branching into the Lambda doublet levels was also investigated, and essentially equal populations of levels of A' and A" symmetry were found. The present results are compared with previous investigations of this reaction and the analogous O(1D)+D2 reaction., (2005 American Institute of Physics.)