Measurement of the absolute Raman scattering cross sections of sulfur and the standoff Raman detection of a 6‐mm‐thick sulfur specimen at 1500 m

The absolute Raman scattering cross sections (σ_RS) for the 471, 217, and 153 cm⁻¹ modes of sulfur were measured as 6.0 ± 1.2 × 10⁻²⁷, 7.7 ± 1.6 × 10⁻²⁷, and 1.2 ± 0.24 × 10⁻²⁶ cm² at 815, 799, and 794 nm, respectively, using a 785‐nm pump laser. The corresponding values of σ_RS at 1120, 1089, and 1081 nm were determined to be 1.5 ± 0.3 × 10⁻²⁷, 1.2 ± 0.24 × 10⁻²⁷, and 1.2 ± 0.24 × 10⁻²⁷ cm² using a 1064‐nm laser. A temperature‐controlled, small‐cavity (2.125 mm diameter) blackbody source was used to calibrate the signal output of the Raman spectrometers for these measurements. Standoff Raman detection of a 6‐mm‐thick sulfur specimen located at 1500 m from the pump laser and the Raman spectrometer was made using a 1.4‐W, CW, 785‐nm pump laser. Copyright © 2010 John Wiley & Sons, Ltd.     

Luminescence and decay times of CsI:In+

Luminescence spectra of single crystals of CsI:In⁺ excited in the A(304 nm), B(288 nm), C(268 nm) and D(257 nm) absorption bands have been studied in the temperature range 4.2–300 K. Excitation in the A band at 4.2 K gives rise to the principal emission at 2.22 eV accompanied by a partly-overlapping weak band at 2.49 eV. An additional emission band at about 2.96 eV is observed on excitation in the B, C or D bands. Yet another emission band located at 2.67 eV is excited only in the D band. The relative intensities of the bands are very sensitive to excitation wavelength as well as to temperature. The origin of all these bands is assigned in terms of a model for the relaxed excited states (RES). All the luminescence spectra were resolved into an appropriate number of skew-Gaussian components. Moments analysis leads to a value of (1.35 ± 0.02) × 10¹³ rad s^-1 for the effective frequency (ω_eff) of lattice vibrations coupled to the RES. At the lowest temperature, the radiative decay times of each of the intracenter emission bands (2.22, 2.49 and 2.96 eV) show a slow decay ( ～ 10–100 μs) and a fast decay ( ～ 10–100 ns). The 2.96 eV band, which is assigned to an emission process which is the inverse of the D-band absorption, exhibits a single decay mode ( ～ 10 μs). The intrinsic radiative decay rates (k₁, k₂), the one-phonon transition rate (K) and the second-order spin-orbit splitting (D) for the RES responsible for the principal emission are: k₁ = (6.0±-0.3)×10³ s^-1, k₂ = (1.33±-0.06)×10⁵ s^-1, K = (2.4±-0.4)×10⁷ s^-1 and D = (13.8±-0.5) cm^-1.     

Variation of potential energy surface height and bound state depth induced by laser phase along the reaction path in atom-molecule reactions: Application to Li + CH<Subscript>4</Subscript> → LiH + CH<Subscript>3</Subscript>

Laser atom-molecule reaction interaction through polarizability and dipole moment contribution leads to potential energy surface barrier reshaping and bound states along the reaction path. The polarizability is maximum in the transition state. We will show here by using gauge representation (electric field gauge) for wave length λ = 20.6 μm, intensity I = 1 × 10¹² W/cm², I = 5 × 10¹² W/cm², I = 1 × 10¹³ W/cm², I = 3 × 10¹³ W/cm², that we can create laser induced potential energy surface barrier reshaping in the transition state region (–1–0.5 a. u.). We illustrate such effects for the LiH + CH₃ ? Li + CH₄ reaction with a barrier using ab-initio methods for calculating the reaction path, polarizability and dipole moment contribution of the atom-molecule reaction.     

Line strengths,spin-splittings,and forbidden transitions in the (101) band of 14N16O2

Measurements of line strengths in the (101) and (111)-(010) bands of ¹⁴N¹⁶O₂ have been made at a resolution of 0.02 cm^?1 in the region 2863 to 2934 cm^?1. The strength data in the (101) band were analyzed to determine a vibrational band strength and coefficients of the F factor. Each subband for K_?1 ≤ 9 was analyzed separately and all the F-factor coefficients in terms of the rotational quantum number, N, were found to be too small to be of significance. However, F was found to be dependent on K_?1 and the experimentally determined subband strengths were least-squares fitted to the expression S_v⁰·F, where S_v⁰ = 68.3 cm^?2 atm^?1 at 296 K and F = 1 + (2.899 × 10^?3)K_?1 + (4.08 × 10^?3)K_?1² ? (2.34 × 10^?4)K_?1³. The integrated strengths for the (101) and (111)-(010) bands were found to be 70.9 ± 2.3 and 2.7 ± 0.3 cm^?2 atm^?1 at 296 K, respectively. Also included in this study are measurements of line center positions in the two bands and spin-splittings in the (101) band. Recent frequency measurements of lines with K_?1 ≤ 8 in the (101) band have been made at a resolution of 0.0033 cm^?1 by V. Dana and J. P. Maillard (J. Mol. Spectrosc.71, 1–4) (1978)) for the region above 2889 cm^?1 and our values are in excellent agreement with theirs. Separations of the split lines measured in this work (K_?1 ≤ 10) agree well with calculated values using expressions which include the η_aaaaK_?1⁴ term with η′_aaaa = ?1.70 ± 0.15 × 10^?4 cm^?1 as derived for the (101) state. Three forbidden (ΔN ≠ ΔJ, ΔK_?1 = 0) transitions in the (101) band were observed with their identifications based on the agreement between measured and calculated line positions and strengths.     

Measurement of Ar(I) and Ar(II) transition probabilities in LTE ARC plasmas

The transition probabilities of two Ar(I) lines and one Ar(II) line have been measured in emission on wall-stabilized argon arc plasmas (0·5×10⁵?p, Nm^-2?3×10⁵; 10,000?T, K?20,000; 10²²?N_e, m^-3?5×10²³) using the “method of best fit (MBF)”. The results (without line-wing correction) are for Ar(I) at 714·7 nm, A_nm=5·66×10⁵ s^-1±5%; for Ar(I) at 430·0 nm, A_nm=3·40×10⁵ s^-1±5%; for Ar(II) at 480·6 nm, A_nm=8·82×10⁷ s^-1±7%. These values were not influenced by deviations from LTE, which have been observed at electron number densities n_e?10²³ m^-3. The small uncertainties were achieved after careful corrections of different sources of error.     

Shock-tube determination of absorption cross sections and A2Δ − X2Π band transition moments of SiH

The overall absorption cross sections and electronic transition moments of the A²Δ ? X²Π band system of SiH have been determined by using an absorption technique with a shock tube at temperatures of 2600–3800 K over the wavelengths of 150–650 nm. Absorption cross sections are shown to be dominated by continua. The possible contributions to the overall cross sections by a low-lying ⁴Σ^- and a high-lying ⁴Σ^- state are discussed. At 200, 228, 340, 405, and 550 nm, the continuum cross sections are (2.9±1.0)×10^-17, (2.0±0.5)×10^-17, (3.2±0.6)×10^-18, (3.8±0.6)×10^-18, and (1.8±0.8)×^-18cm², respectively. The overall emission intensity and the Si+H→SiH+hv radiative recombination rate are (6.7± 2.3)×10^-35(3500/T)^0.7(Si)(H) watt-cm^-3 and (1.3±0.4)×10^-17(3500/T)^1.1(Si)(H) cm^-3-s^-1, respectively. The A ? X transition moments are 0.12±0.04a.u. for the (0, 0) and (1, 1) bands. The intensity of each branch in the A ? X (0, 0) band follows approximately the prediction based on the Hönl-London factors of Kovacs. The data are applied to the study of the flow field around a spacecraft entering the Jovian atmosphere.     

Investigation of third-order optical nonlinearity in KBe2BO3F2 crystal by Z-scan

The third-order optical nonlinearity of deep-ultraviolet (DUV) nonlinear optical (NLO) crystal KBe₂BO₃F₂ (KBBF) was investigated using single-beam Z-scan technique for the first time. The Z-scans were performed on a c-cut KBBF crystal and a KBBF prism-coupling device (PCD) with picosecond pulses at 355?nm. No two-photon absorption was observed in the experiment. The measured nonlinear refraction index n ₂ showed positive signs, indicating self-focusing Kerr effects. The n ₂ values were estimated to be (1.75±0.35)×10^?15?cm²/W with the c-cut sample and (1.85±0.37)×10^?15?cm²/W with the PCD, corresponding to the third-order nonlinear optical susceptibilities $\chi_{\mathrm{eff}}^{(3)}$ of (0.99±0.20)×10^?13?esu and (0.94±0.19)×10^?13?esu, respectively. The results are expected to promote the investigation of frequency conversion processes with ultra-short laser in KBBF crystal.     

The Pt(110) phase transitions: A study by rutherford backscattering,nuclear microanalysis,LEED and thermal desorption spectroscopy

The adsorbate induced (1×2) (1×1) (2×1)p1g1 phase transitions on Pt(110) have been studied by Rutherford backscattering (RBS), nuclear microanalysis (NMA), LEED and thermal desorption spectroscopy. RBS data indicate that any displacement of the surface atoms from their expected bulk-like lattice sites in the (1×2) phase is ? 0.002 nm laterally and ? 0.007 nm vertically. This contraint eliminates models for the reconstruction which involve significant lateral displacements (e.g., the paired-atom or hexagonal overlayer models). The RBS data are consistent with both the rumpled model with up/down displacements not exceeding ~0.007 nm and the missing row model with an unrelaxed surface in which the out-of-plane vibrational amplitude is slightly enhanced. A c(8×4) phase, produced by CO (or NO) exposure at T?250 K, has also been characterized by RBS which demonstrated that 0.92×10¹⁵ Pt cm^?2 move on average by ~0.017 nm laterally out-of-registry with the bulk upon formation of this phase. The values of the saturation adsorbate coverages at T?200K were determined by NMA to be 0.92 ± 0.05×10¹⁵, 1.0 ± 0.06×10¹⁵ and 1.07 ± 0.10×10¹⁵ CO molecules, NO molecules and D atoms, respectively, per cm². The value of the saturation coverage by CO (θ = 1.0) supports recent models of the (2×1)p1g1 overlayer. The isosteric heat of adsorption of CO is 160 ± 15 kJ mol^?1 in the range 0.2?θ?0.5.     

The analysis of symmetric rotor Raman spectra: The pure rotational spectrum of 11BF3

The pure rotational Raman spectrum of ¹¹BF₃ has been photographed. Great care was taken in the analysis to consider all the unresolved components under each observed Raman line profile. If this is ignored, systematic errors result. The final set of molecular constants obtained was B₀ = 0.34502(±3 × 10^?5)cm^?1, D_J = 4.38(±0.10) × 10^?7cm^?1, and D_JK = ?9.1(±1.0) × 10^?7cm^?1.     

Destruction of26Al in explosive nucleosynthesis

The²⁶Al(n, p)²⁶Mg reaction has been studied using neutron spectra which closely resembled Maxwell-Boltzmann (M.-B.) distributions with thermal energies ofkT=40 ×10^?6, 31 and 71 keV and also forE _n =270–350 keV. These energies correspond to stellar temperaturesT ₉=4.6×10^?7, 0.36, 0.82 and 3.1–4.1, whereT ₉ is in units of 10⁹ K. The partial cross sections for thep ₀-(p ₁-)transition are found to equal 26±10(1,850 ±150), 13±6(124±17), 16±13(84±14) and 21±8(72±15) mb for the above neutron spectra, respectively. The astrophysical reaction rate is determined for the combinedp ₀- andp ₁-transitions to beN _A 〈σν〉=(0.324±0.026, 20.5±2.7, 22.6±4.3 and 38.7±11.1) ×10⁶ cm³ mole^?1 s^?1. The results are compared with previous investigations and with statistical model calculations.     

Measurements of emission coefficient for continuum radiation from shock-heated krypton plasmas

Using a shock tube, the ξ factor of krypton has been determined at λ = 456.1 nm by observations of the continuum radiation and simultaneous interferometric measurements of the electron number density. For the electron-density range used (1×10¹⁶cm^-3?n_e?4×10¹⁶cm^-3), we obtain an increase in the ξ factor for decreasing electron densities. These results are compared with theoretical and other experimental data.     

Measurement of the absolute Raman scattering cross section of the 1584‐cm−1 band of benzenethiol and the surface‐enhanced Raman scattering cross section enhancement factor for femtosecond laser‐nanostructured substrates

The absolute Raman scattering cross section (σ_RS) for the 1584‐cm⁻¹ band of benzenethiol at 897 nm (1.383 eV) has been measured to be 8.9 ± 1.8 × 10⁻³⁰ cm² using a 785‐nm pump laser. A temperature‐controlled, small‐cavity blackbody source was used to calibrate the signal output of the Raman spectrometer. We also measured the absolute surface‐enhanced Raman scattering cross section (σ_SERS) of benzenethiol adsorbed onto a silver‐coated, femtosecond laser‐nanostructured substrate. Using the measured values of 8.9 ± 1.8 × 10⁻³⁰ and 6.6 ± 1.3 × 10⁻²⁴ cm² for σ_RS and σ_SERS respectively, we calculate an average cross‐section enhancement factor (EF) of 0.8 ± 0.3 × 10⁶. Copyright © 2009 John Wiley & Sons, Ltd.     

Magneto-acoustic attenuation in AuSb2

Quantum oscillations in the ultrasonic attenuation in AuSb₂ were studied as a function of temperature, magnetic field and crystal orientation. The effective masses of the carriers associated with the F₅ and F₆ oscillations were measured in a (110) plane. For the F₅ oscillations, the Dingle temperature and apparent magnetic breakdown field appear to depend strongly upon orientation. For the F₆ oscillations, however, there were no signs of magnetic breakdown up to the highest magnetic fields available (70 kOe) and the Dingle temperature was roughly independent of orientation. From the acoustic velocities, the elastic constants were determined at 77 K: C₁₁ = (14·7 ± 0·9) × 10¹¹ dyne/cm², C₁₂ = (6·0 ± 0·9) × 10¹¹ dyne/cm², and C₄₄ = (2·59 ± 0·06) × 10¹¹ dyne/cm². These elastic constants give an adiabatic compressibility K_s = (1·13 ± 0·12) × 10^?12 cm²/dyne and a Debye temperature ?_D = (203 ± 15) K.     

Low-temperature absorption contour of the ν3 band of SF6

A band contour analysis is carried out for the ν₃ absorption in SF₆. Values of ΔB = ? (1.0 ? 1.5) × 10^?4cm^?1, ζ₃ = 0.701, and ν₀ = 948.2cm^?1 are found. Tentative assignments are given for the SF₆ rotational states which are pumped by the P(14) through P(22) lines of the CO₂ laser.     

Tunable laser Stark-difference spectra of CD3OH

We present Doppler resolution limited spectra of the P(J) and R(J) multiplets for J ≦ 10 of the 10-μm CO stretch band of ¹²CD₃¹⁶OH using a tunable diode laser. Relative frequencies within the multiplets accurate to ±0.0002–0.0005 cm^?1 are obtained, but no absolute frequencies are given. We are able to assign most of the hindered rotation and K substructure in these multiplets. The assignments are based on analyses of Stark-difference spectra combined with the ground-state microwave data and the intensity variations which are expected theoretically. The ground and excited state A, K = 1 asymmetry splitting parameters are measured to be δ₁″ = (8.5450 ± 0.0080) × 10^?3cm^?1 and δ₁′ = (9.7706 ± 0.0080) × 10^?3cm^?1, respectively. The ground-state value agrees well with the microwave results. A rapid-scan system for recording data and a computer-aided technique for calibrating and plotting the spectra are described.     

Influence of Na-related defects on ArF laser absorption in CaF2

ArF laser pulse transmission through commercial high purity CaF₂ is determined by measuring the energy of each pulse before and behind the sample up to an incident fluence H of 10 mJ/cm². The steady state transmission of ArF laser pulses decreases with increasing fluence. The related absorption coefficients α ^st(H) are proportional to H and rationalized by effective 1- and 2-photon absorption coefficients 2.4×10^?4 cm^?1≤α ^eff≤16.8×10^?4 cm^?1 and 1.7×10^?9 cm?W^?1≤β ^eff≤9.3×10^?9 cm?W^?1, respectively. The α ^eff and β ^eff values increase with the Na content of the CaF₂ samples as identified by the fluorescence of Na-related M _Na centers at 740 nm. This relation is simulated by a rate equation model describing the ArF laser induced M _Na generation in the dark periods between the laser pulses and their annealing during laser irradiation. M _Na generation starts with intrinsic 2-photon absorption in CaF₂, yielding self-trapped excitons (STE). These pairs of F and H centers move upon thermal activation and the F centers combine with F _Na to form M _Na centers. M _Na annealing occurs by its photo dissociation into a pair of F and F _Na centers.     

ESR study of vanadyl ion in trisodium citrate pentahydrate

ESR study of VO²⁺ doped trisodium citrate pentahydrate is undertaken at room temperature. The observed spectra are correlated with the available crystal structure data and are fitted to a spin Hamiltonian of orthorhombic symmetry with g_x = 1.998 ± 0.001, g_y = 1.992 ± 0.001, g_z = 1.934 ± 0.001, A_x = (70.0 ± 1) × 10^-4cm^-1, A_y = (66.6 ± 1) × 10^-4cm^-1 and A_z = (175.4 ± 1) × 10^-4cm^-1. The covalency and Fermi contact parameters are evaluated and compared with those of VO²⁺ in other lattices.     

表面层对1 064 nm高反射镜损伤阈值影响

 采用电子束蒸发的方法制备了３种具有不同表面层材料及结构的中心波长为1 064 nm的零度高反镜,３种膜系表面层分别为1/4波长光学厚度的HfO₂,1/2波长光学厚度的SiO₂,以及1/4波长光学厚度的SiO₂。光谱测试表明：三者在1 064 nm处均有较高的反射率（高于99.8%）,利用热透镜的方法测量得到３个膜系辐照激光正入射情况下,薄膜对光的吸收比例分别为3.0×10^-6,5.0×10^-6和6.5×10^-6,其损伤阈值分别为32.5,45.2和28.4 J/cm²。并在膜层内部电场分布和膜层材料物理特性的基础上分析了３种不同表面层膜系吸收和损伤阈值差别的原因。     

Inverse Raman spectrum of the ν1-fundamental of CF4

We have obtained fully resolved spectra of the ν₁ (Q-branch) band of CF₄ at a pressure of 4 Torr using a variation of stimulated Raman spectroscopy. With an experimental resolution of ≤0.004 cm^?1, no detectable tensor splitting of the rotational levels exists up to J = 55. The spectrum is readily fit with a band origin α = 909.0720 cm^?1 and a single rotational term β ? β₀ = ?3.417 × 10^?1cm^?1. We have also observed an underlying hot band, which we tentatively assign as the ν₁ + ν₂ ← ν₂ transition, with α′ = 909.1997 cm^?1 and (β ? β₀)′ = ?3.405 × 10^?4cm^?1.     

Vibrational spectra and force constants of symmetric tops: High-resolution spectra of H374Ge35Cl in the ν1ν4 region near 2100 cm−1

The gas-phase infrared spectrum of monoisotopic H₃⁷⁴Ge³⁵Cl has been studied in the ν₁, ν₄ region near 2100 cm^?1 with a resolution of 0.008 cm^?1. Rotational fine structure for ΔJ = ±1 branches has been resolved for both fundamentals. ν₁ (a₁), 2119.977 03(19) cm^?1; and ν₄ (e), 2128.484 65(8) cm^?1 are weakly coupled by Coriolis x,y resonance, Bξ_1,4^y 2.6 × 10^?3 cm^?1, and l-type resonance within ν₄, q₄⁽⁺⁾ ?8.4 × 10^?6 cm^?1, has been observed. An extended Fermi resonance with ν₅^±1 + 2ν₆^±2, which mainly affects the kl = ?14 and ?15 levels of ν₄, has been detected and analyzed. In addition, several weak and local resonances perturb essentially every K subband of ν₄ and some of ν₁, and a qualitative model is proposed to account for the features observed in the spectrum. Disregarding the transitions involved in local perturbations, the rms deviation of the fit to the remaining 2021 lines is σ = 1.34 × 10^?3 cm^?1.