[en] Quantum yields for the production of H(D) atoms in the reaction of singlet-excited metastable molecular nitrogen, N₂(a ¹Πg, ν=0), with H₂ and D₂ were determined by analyzing the temporal profiles of N₂(a, ν=0) and H(D)-atom densities after pulsed excitation. N₂(a, ν=0) was produced by the two-photon excitation of ground-state N₂, while H(D) atoms were detected by two-photon laser-induced fluorescence. N₂(a, ν=0) was detected by laser-induced fluorescence utilizing the N₂(b^'1Σu⁺, ν=7) state as an upper-state. The H(D) atom yields are 0.5 ± 0.1 for H₂ and 0.4 ± 0.1 for D₂, suggesting that the near resonant relaxation to another metastable molecular nitrogen, N₂(a^'1Σu^-), is also important. The production of N₂(a^'1Σu^-) in collisions with H₂(D₂) was confirmed by measuring the H₂(D₂) pressure dependence of the two-photon laser-induced fluorescence signal of N₂(a^'1Σu^-, ν=0) via the N₂(b ¹Πu, ν=1) state

[en] Radical species play key roles in chemical vapor deposition (CVD) processes, including catalytic CVD (hot-wire CVD), and evaluating their densities in the gas phase is important in understanding the underlying mechanisms and controlling the processes. There are many diagnosis techniques to detect radical species. Among them, photon-in–photon-out techniques, including one- and two-photon laser-induced fluorescence and photo-absorption, can be utilized under the low vacuum conditions typical in CVD processes. Highly sensitive, quantitative, state-specific, real-time, and non-intrusive detection is possible with these techniques; even spatial resolution can be obtained in some cases. At the same time, however, we should know the drawbacks and the limitations of such techniques. A compilation of the radical species detected so far in catalytic CVD processes is presented in a table. - Highlights: • Radical species play key roles in chemical vapor deposition (CVD) processes, including catalytic CVD (hot-wire CVD). • The principles of laser spectroscopic techniques, which are essential in radical detection in CVD processes, are presented. • A compilation of the radical species detected so far in catalytic CVD (Hot-wire CVD) processes is presented in a table

[en] The decomposition processes of PH_3 on heated W, Mo, Ta, and Ir surfaces were studied using mass spectrometric and laser spectroscopic techniques. For all wire materials, the decomposition efficiency saturated to around 50% at high wire temperatures. The P-atom density also saturated showing only minor dependence on the wire materials. At lower temperatures, however, the production rate of P atoms on Ta was higher than that on W, while that for Mo was lower, suggesting that the decomposition processes are not thermal but catalytic. The production rate on Ir was similar to that on W. Possible decomposition mechanisms are discussed

[en] Metal wires, such as W, Mo, and Ta, can be boronized to become sinks of B atoms by heating them in the presence of a mixture of H₂ and H₃NBH₃ or (BH)₃(NH)₃. These boronized wires behave as sources of B atoms when heated in vacuum. The density of B atoms released to the gas phase increases with the addition of H₂ and can be > 10¹¹ cm⁻³, which is enough for surface doping. The release is stable and continues for more than several hours when boronized for 1 h. Since the metal wires are not nitrided, contamination by N atoms is not expected. H₃NBH₃ and (BH)₃(NH)₃ are not explosive, and wires boronized by these species can be used as safe and contamination-free sources of B atoms for surface doping. - Highlights: • Metal wires can be boronized by heating in the presence of H₃NBH₃ or (BH)₃(NH)₃. • These boron compounds are non-explosive. • These boronized wires behave as sources of B atoms when heated. • The B-atom density released from boronized wires is enough for surface doping. • By placing substrates after boronization, N-atom contamination can be avoided.

[en] The bimolecular rate constants for the reactions of ground state atomic nitrogen with hydrogen halides and deuterium iodide were measured by employing a pulse radiolysis-resonance absorption technique. As for the reactions of hydrogen iodide and deuterium iodide, the temperature dependence was also measured; it was found that the rate constants were well expressed by the following Arrhenius expressions: k(N + HI) = (3.6 ± 0.6) x 10⁵ exp[-(1530 ± 50)/T]; k(N + DI) = (1.0 ± 0.4) x 10⁵ exp[-(1460 ± 130)/T], in units of m³mol^-1s^-1. The preexponential factors for these reactions are much smaller than the semiempirically calculated ones. These small preexponential factors suggest that these reactions proceed non-adiabatically. The rate constants for hydrogen bromide and hydrogen chloride were found to be very small. (author)

[en] Rate constants for the reactions N(2²D) + H₂(D₂) and N(2²P) + H₂(D₂) have been measured by employing a pulse radiolysis-resonance absorption technique at temperatures between 213 and 300 K. The rate constants were expressed by the following Arrhenius equations:k_N(²D)+H2 = 4.6 x 10^-11 exp(-8.8 x 10²/T), k_N(²D)+D2 = 3.9 x 10^-11 exp(-9.7 x 10²/T), k_N(²P)+H2 = 3.5 x 10^-13 exp(-9.6 x 10²/T) and k_N(²P)+D2 = 1.9 x 10^-13 exp(-9.2 x 10²/T), in units of cm³ s^-1. The results for N(²P) suggest that the main exit channels are not chemical reactions to produce NH (ND) radicals. The Arrhenius parameters for N(²D)+H₂(D₂) are compared with the results of transition-state theoretical calculations as well as those of quasiclassical trajectory calculations on the basis of extended LEPS potential-energy surfaces. (Author)

[en] The deactivation processes of Cd(5³P₁) and Cd(5³P₀) by H₂ and D₂ were examined by employing a laser excitation-depletion technique. The concentration of the ground-state Cd(5¹S₀) atoms was measured in both the presence and absence of an intense saturable pump laser beam. In the presence of a pump laser, the concentration decreased in accordance with the production of CdH(CdD). From this decrease, the branching ratios for the production of CdH(CdD) could be determined. The depletion was unaffected when N₂ was added. This suggests that the branching ratios are the same for Cd(5³P₁) and Cd(5³P₀), although the production of CdH(CdD) is endothermic for Cd(5³P₀). The branching ratios were 0.81±0.04 for H₂ and 0.76±0.06 for D₂. The efficient production of CdH(CdD) from not only Cd(5³P₁), but also Cd(5³P₀), can be accounted for by correlational considerations. (author)

[en] Cross sections for the quenching of N(2²P) by a variety of simple organic and inorganic compounds have been determined by using a pulse radiolysis-optical absorption technique. It was found that N(2²P) is less reactive than N(2²D) in every case, despite its higher energy. The quenching cross sections for unsaturated hydrocarbons were found to be about one tenth of that for gas kinetic collisions, while those for saturated hydrocarbons and most inorganic substances were much smaller. The quenching cross sections for alkane hydrocarbons increase with the number of C-H bonds, and show a minor dependence on C-H bond strengths. (author)

[en] The rate constants of the reactions of hydrogen and deuterium atoms with four ketenes have been measured using a pulse radiolysis-resonance absorption technique. For hydrogen atoms, the temperature dependence was also examined in the range of 240-440K. The rate constants were well expressed by these Arrhenius equations: k(H+ketene)=3.9 x 10⁶ exp(-975/T); k(H+methylketene)=7.4 x 10⁶ exp(-881/T); k(H+ethylketene)=4.4 x 10⁶ exp(-728/T); k(H+dimethylketene)=6.0 x 10⁶ exp(-773/T), in units of m³mol^-1s^-1. No isotope effect between H and D atoms could be observed except for the gas-kinetic-collision frequency. (author)

[en] The deactivation processes of N₂(a' ¹Σ_u^-, ν=0), the lowest metastable singlet-state molecular nitrogen, by H₂O, D₂O, and HOD were investigated. The overall rate constants as well as the quantum yields for the production of H(D) atoms were determined. N₂(a', ν=0) was produced by energy transfer from N₂(a ¹Π_g, ν=0), while N₂(a, ν=0) was produced by a two-photon excitation of the ground-state N₂. The rate constants for the deactivation by H₂O and D₂O were determined to be (4.22 ± 0.27) x 10^-10 and (4.21 ± 0.11) x 10^-10 cm³ s^-1, respectively, by measuring the decay profiles of N₂(a, ν=0) under equilibrated conditions. The quantum yields for the production of H(D) atoms were determined to be 0.9_-0.2^+0.1 both for H₂O and D₂O under the assumption that the only exit for H₂(D₂) is the production of two H(D) atoms. In a reaction with HOD, the yield ratio of [H]/[D] was measured to be 1.0±0.1. This lack of the isotope effect suggests that the decomposition proceeds by forming bound intermediate complexes, such as HNNOD and DNNOH. (author)