Measurements of pressure-induced shifts in the 1-0 and 2-0 bands of HF and in the 2-0 bands of H35Cl and H37Cl

Fourier absorption spectra of HCl and HF measured at room temperature and low pressures were found to show evidence of pressure-induced shifts of the spectral lines at gas pressures of only 10 torr. Self-induced shifts were measured for the HF 2-0 band and for the H³⁵Cl and H³⁷ 2-0 bands. There were also measured in the same spectra shifts in the HF 2-0 band due to HCl and shifts in both HCl bands due to HF, with indications of shift oscillation due to near-resonant dipole-dipole interactions between HCl and HF. Separate measurements were made of pressure-induced shifts in the HF 1-0 and 2-0 bands and in both isotopic HCl bands, using separately argon, neon, nitrogen and carbon dioxide as the perturbing gases.     

Pressure broadening in the 0–4 through 0–7 overtone bands of H35Cl and H37Cl

We have measured the pressure broadening coefficients of a number of rotation-vibration lines in the 0–4 through 0–7 overtone bands of HCl utilizing a Fourier transform spectrometer and a 409 m path length White cell. These data, when included with previous measurements on the fundamental and lower overtone bands, show a systematic variation of pressure broadening with increasing overtone band. This result reflects a change in the collision dynamics between molecules in the upper state of the transition with ground state molecules.     

Absolute frequency measurements of the 0002-0000, 2001-0000, and 1201-0000 bands of N2O by heterodyne spectroscopy

The absolute frequencies of 39 lines in the 00⁰2-00⁰0, 20⁰1-00⁰0, and 12⁰1-00⁰0 bands of N₂O in the range 4300–4800 cm^?1 have been measured by heterodyne frequency techniques. The lines were each measured in Doppler-limited absorption, with a color-center laser as a tunable probe of the N₂O and two stabilized CO₂ lasers as reference frequencies. New rovibrational constants have been fitted to these measurements. Tables of calculated transition frequencies are given, with estimated absolute uncertainties as small as 10^?4 cm^?1. The pressure shifts of four lines have been measured, and the values fall within the range of 0 to ?2 MHz/kPa (0 to ?0.2 MHz/Torr).     

Temperature dependence of rare gas broadening and shifting of first harmonic lines of H35Cl

Widths and shifts of HCl vibration-rotation lines, pressurized by rare gases, have been measured for the 0–2 band as functions of temperature. The results reported here complement previously published results on the fundamental band. The model of Smith, Giraud and Cooper is used to calculate widths and shifts; good agreement is obtained between experiment and theory. Problems concerning the accuracy of available potential energy surfaces and the calculation of differential cross sections are discussed briefly.     

Bounds on the π0π0 amplitude

A new approach to the problem of constraining the scattering amplitudes by using axiomatically proved properties of unitarity, analyticity and crossing is developed. It is applied to obtain absolute and semi-phenomenological bounds on the π⁰π⁰ amplitude at points lying on the Mandelstam triangle, in particular at the physical threshold (scattering length) and at the symmetric point (which is used to define the coupling constant). We have already reported a less general and powerful approach which improved the previous results in this field. The present version, which constitutes a noticeable generalization of the method, allows a new improvement of the bounds, both absolute and semi-phenomenological.     

Investigation of the reaction 37Cl(n, γ)38Cl

With Ge(Li) detectors the γ-radiation following thermal-neutron capture in natural and in ³⁷Cl enriched targets was studied. A total of 79 γ-lines has been assigned to the ³⁷Cl(n, γ) reaction and 64 of these lines have been placed in a decay scheme of ³⁸Cl. The excitation energies of 24 bound states of ³⁸Cl have been determined with 0.09–1.2 keV errors. The neutron separation energy of ³⁸Cl is 6107.7 ± 0.4 keV. A strong correlation between reduced stripping widths and (n, γ) primary reduced widths was found for the l_n(d, p) = 1 states if, instead of the Weisskopf reduction factor E_γ^?3, a factor E_γ^?1.2 was used.     

H- formation in H0++ Mg collisions

Absolute differential and total cross sections for H^- formation in H⁰ + Mg collisions have been measured over the energy range 1.0–5.0 keV. The differential cross section is strongly peaked in the forward direction and exhibits a shoulder at low energies. The total cross section has two pronounced maxima, and this structure is discussed.     

Pure rotational spectra of 32SF535Cl, 32SF537Cl,and 34SF535Cl up to 300 GHz

Pure rotational spectra of the three molecules ³²SF₅³⁵Cl, ³²SF₅³⁷Cl, and ³⁴SF₅³⁵Cl in their ground vibrational states have been observed up to 300 GHz (8 < J < 80). Molecular parameters have been computed with good accuracy for the three isotopic species. The “K-type” splitting characteristic of molecules belonging to the C_4v symmetry group has been clearly seen and measured.     

The fluorescence and IR energy deposition from from CO2 laser irradiation of SF6−H2 mixtures

The multiple photon excitation and dissociation of SF₆ and hydrogen mixtures is measured by using simultaneously pulsed optoacoustic detection to monitor the energy deposition and time resolved HF fluorescence to monitor the production of vibrationally hot HF. From these studies we deduce that at least three mechanisms lead to production of vibrationally excited HF. One mechanism produces free F from the unimolecular laser-induced decomposition of SF₆. The second mechanism involves the reaction between two vibrationally hot SF₆ molecules to produce free F. In both of these cases the F atom subsequently react with H₂ to produce vibrationally hot HF. The third involves the reaction between a vibrationally hot SF₆ molecule and a hydrogen molecule producing vibrationally hot HF directly.     

H+2，H+3团簇离子在沟道条件下的背散射 质子产额测量

采用卢瑟福背散射方法，测得了每质子能量为650 keV的H⁺₂，H+₃团簇离子在Si晶体<100>和<110>沟道条件下的质子背散射能谱.结果发现，由于H⁺₂，H⁺₃团簇在晶体中的库仑爆炸和团簇效应，H⁺₂的背散射质子产额大于H ⁺的背散射产额，而H^{+< 关键词： 团簇 沟道效应 库仑爆炸 背散射}     

Strengths of (p, γ) resonances in 33Cl, 35Cl and 28Si

Absolute strength measurements have been performed for the E_p = 580 and 588 keV ³²S(p,γ)³³Cl, E_p = 1214keV³⁴S(p,γ)³⁵Cl and E_p = 633 and 744 keV²⁷Al(p,γ)²⁸Si resonances with a Ge(Li) detector. Results are discussed with regard to the decay of isobaric analog resonances in ³⁵Cl and ³⁷Cl.     

Ionization by H+2. Molecular effect

The molecular effect in the ionization of inner shell electrons of aluminum atoms by energetic H⁺₂ molecules has been calculated. We distinguish between the molecular effect in Al and Al₂O₃. We conclude that in the case of Al the protons of the cluster have a definite orientation but in the case of Al₂O₃ the orientation is at random.     

Determination of A0 for CH335Cl and CH337Cl from the ν4 infrared and Raman bands

The ν₄ infrared and Raman bands of CH₃Cl were analyzed simultaneously. A direct fit yielded a complete set of constants for CH₃³⁵Cl, including A₀ = 5.20530 ± 0.00010 cm^?1 and D_K = (8.85 ± 0.13) × 10^?5cm^?1. For CH₃³⁷Cl an incomplete set of constants was obtained from the infrared band, and A₀ = 5.2182 ± 0.0010 cm^?1 was estimated by curve fitting of the Raman spectrum. The resulting equilibrium structure is $\text{r(}\text{CH) = 1.0854 ± 0.0005}\text{A}\text{?}$, $\text{r(}\text{CCl) = 1.7760 ± 0.0003}\text{A}\text{?}$, and <(HCH) = 110°.35 ± 0°.05.     

The break-up reaction p0 + d → p1 + p2+ n at E0 = 16 MeV

The break-up reaction p₀ + d → p₁ + p₂ + n has been studied at E₀ = 16 MeV in kinematically complete p₁-p₂ coincidence experiments with special regard to n-p final-state interactions (f.s.i.) and p₁-p₂ quasifree scattering (q.f.s.). The absolute differential cross section has been measured for n-p f.s.i. c.m. production angles from 60° to 140° and for four pairs of angles with strong contributions due to q.f.s. Calculations with separable nucleon-nucleon potentials based on the Faddeev equations are in good agreement with the data obtained. In general, the shape of the experimental differential cross section is well reproduced. Discrepancies of up to 30 % in the worst cases arise between the absolute values of the theoretical predictions and the experimental data.     

Formation of aligned silicon-nanowire on silicon in aqueous HF/(AgNO3 + Na2S2O8) solution

Highly oriented silicon nanowire (SiNW) layer was fabricated by etching Si substrate in HF/(AgNO₃ + Na₂S₂O₈) solution at 50 °C. The morphology and the photoluminescence (PL) of the etched layer as a function of Na₂S₂O₈ concentration were studied. The SiNW layers formed on silicon were investigated by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). It was demonstrated that the morphology of the etched layers depends on the Na₂S₂O₈ concentration. Room-temperature photoluminescence (PL) from etched layer was observed. It was found that the utilisation of Na₂S₂O₈ decreases PL peak intensity. Finally, a discussion on the formation process of the silicon nanowires is presented.     

Spin and parity assignments for 35Cl levels from the 31P(α, p)34S reaction

³⁵Cl states at excitation energies between 9.9 and 11.8 MeV have been identified through sharp resonances in the ³¹P(α, p_o)³⁴S excitation functions at 25°, 105° and 155° for E_α = 3.25–5.50 MeV. Forty-eight on-resonance angular distributions, normalized to an absolute cross section scale, have been subjected to single-level and two-level analyses resulting in spin and parity assignments for each resonance. Approximately half the resonances were of the pure single-state type, having unique angular distribution shapes. Data from 12 resonances of an earlier experiment ¹) were analyzed with the same theory, extending the diagnostics down to a ³⁵Cl excitation energy of 9.1 MeV. A set of optical potentials consistent in all four reactions that this experimental program encompasses has been incorporated in the present analysis. Validity of the optical potential is demonstrated for α-particles elastically scattered by ³¹P.     

The reaction 35Cl(n,γ)36Cl studied with non-polarized and polarized thermal neutrons

The γ-radiation following capture of non-polarized and polarized thermal neutrons in ³⁵Cl has been investigated. Of the 420 γ-rays ascribed to the ³⁵Cl(n,γ)³⁶Cl reaction, 236 have been placed in a ³⁶Cl decay scheme. The branching ratios and the excitation energies (with 0.04–0.9 keV errors) of 72 bound states have been determined. Unambiguous spin assignments are given for 11 levels. The multipole mixing ratios for some primary γ-ray transitions have been determined. There exists a significant correlation between (d, p) stripping strengths and (n, γ) reduced primary transition probabilities for transitions to l_n(d, p) = 0 levels.     

Widths and shifts of H35Cl lines in the fundamental band induced by argon and xenon at low temperatures

We have measured, at high resolution (0.024cm^-1), the linewidths and shifts in the fundamental band of H³⁵Cl broadened by argon (up to 5 bars) and xenon (up to 4 bars) at low temperatures (between 298 and 163 K). The experimental results have been compared with calculated data derived from the Anderson-Tsao-Curnutte theory using the Tipping-Herman potential.     

Simplified method to prepare atomically-ordered TiO2(1 1 0)-(1 × 1) surfaces with steps and terraces

An effective way to prepare atomically-ordered rutile TiO₂(1 1 0) surfaces that have distinct step and terrace structures suitable for oxide thin film deposition is demonstrated. Only a two-step procedure, consisting of 20% HF etching and UHV-annealing at 1100 °C, was required to yield a clean (1 × 1) structure with step and terrace structures. Investigation of the surface using scanning tunneling microscopy, low-energy electron diffraction, and Auger electron spectroscopy reveals that carbon contamination is removed at around 800 °C, and straight steps with clear terraces appear at around 1000 °C.     

Absolute measurement of an atomic cascade rate using a two photon coincidence technique. Application to the 4p21S0 -4s4p 1P1 -4s21S0 cascade of calcium excited by a two photon absorption

The two photon coincidence technique yields an absolute measurement of a cascade decay rate without knowing the detection efficiency of each detector. This method is applied to calcium atoms in an atomic beam excited to the 4p²¹S₀ state, and decaying via the resonant ¹P₁ state; it yields the excitation rate of the upper 4p²¹S₀ level. Since the excitation process (two photon absorption) is controlled, one can compute the excitation rate of the upper level as a function of the transition probabilities in the cascade. The lower transition is well known and we can therefore deduce the transition probability for the 4p²¹S₀ -4s4p ¹P₁, transition which previously had not been accurately determined. The preliminary measurements yield a line strength s = 0.98 ± 0.3 au in good agreement with a recent measurement of the lifetime of the 4p²¹S₀ state.