Evidence of complex positron-ammonia interaction in ammonia gas

Positron annihilation in ammonia gas at temperatures of ?19°C, 22,5°C, and 95°C in the density range 1.76 × 10^?4 g/cm³ to 6.63 × 10^?3 g/cm³ is investigated. ¹Z_eff for orthopositronium annihilation is 0.58 ± 0.04 Z_eff/ Z for positrons not forming positronium varies from about 117 to 1329.     

The ring puckering vibration of 3,3-dimethyloxetan

The far-infrared vapor phase spectrum of 3,3-dimethyloxetan, consisting of a series of overlapping B contours around 90 cm^?1 and a sequence of A contours upward of 130 cm^?1, has been assigned in terms of Δv_p = 1 and 2 transitions in the ring puckering mode. The constants in the potential function, V(Z) = A(Z⁴ + BZ²), Z the reduced puckering coordinate, are calculated to be A = 19.24 cm^?1 and B = ?3.106, and the inversion barrier 46.4 cm^?1.     

Submillimeter wave spectrum and molecular constants of N2O

The submillimeter wave spectrum of the N₂O molecule has been investigated within the 375–565 GHz frequency range with a sensitivity better than 10^?8 cm^?1. The measured frequencies include 161 lines with intensities γ ? 10^?6 cm^?1 belonging to 22 spectroscopically different species of the molecule (specifically, the ground and some excited vibrational states of the five most abundant isotopic species of the molecule in natural abundance) with a statisticall and systematic error of the order of magnitude 10^?8. Rotational and two centrifugal stretching constants could be determined for each spectroscopic species. For each isotopic species observed, we have made a general analysis of the spectrum in different vibrational states bearing in mind resonance effects. The total number of the rotational and rovibrational constants obtained exceeds 40.     

Vibrational spectra and ring-puckering of 2-cyclopenten-1-ones

The mid-infrared, far-infrared, and Raman spectra of 2-cyclopenten-1-one and 2-cyclopenten-1-one-5, 5-d₂ have been recorded. Assignments for each of the thirty vibrational fundamentals have been made for the two molecules. Several ring-puckering transitions were observed in the far-infrared spectrum of each molecule. From these were determined potential functions which establish the planarity of the ring system. The potential functions in reduced form derived for the hyride and deuteride are V = 15.0(Z⁴ + 8.0Z²) cm^?1 and V = 14.2(Z⁴ + 8.8Z²) cm^?1, respectively.     

Far-infrared spectrum and ring-puckering of 3-cyclopenten-1-one

The far-infrared spectrum of 3-cyclopenten-1-one in the vapor phase has been recorded and a broad absorption with a series of several Q branches was observed in the 80–120 cm^?1 region. This series of transition frequencies resulting from the ring-puckering vibration was fitted by the single minimum potential function V = 11.31 (Z⁴ + 12.56 Z²) cm^?1, which is characteristic of a planar ring structure. The origin of the potential function for this molecule and related molecules is discussed.     

Measurement of integrated intensities of acetylene bands at 3·04, 7·53 and 13·7 μm

Integrated intensities of acetylene bands at 3·04, 7·53 and 13·7 μm have been measured at 300°K using the Wilson-Wells-Penner-Weber technique and a spectral resolution of 0·6 cm^?1. Our best estimates of the intensities are 294 ± 6 cm^?2atm^?1 for the 3·04 μ bands, 87 ± 2 cm^?2atm^?1forthe 7·53 μband and 729 ± 28 cm^?2atm^?1 for the 13·7 μ band at 300°K.     

Structural and vibrational properties of PVT grown Bi2Te3 microcrystals

High-quality Bi₂Te₃ microcrystals have been grown by physical vapor transport (PVT) method without using a foreign transport agent. The microcrystals grown under optimal temperature gradient are well facetted and they have dimensions up to ～100 μm. The phase composition of grown crystals has been identified by X-ray single crystal structure analysis in space group R3?m, a=4.3896(2) Å, b=30.5019(10) Å, Z=3 (R=0.0271). Raman microspectrometry has been used to describe the vibration parameters of Bi₂Te₃ microcrystals. The FWHM parameters obtained for representative Raman lines at 61 cm^?1 and 101 cm^?1 are as low as 3.5 cm^?1 and 4.5 cm^?1, respectively.     

High-resolution measurement and analysis of the infrared spectrum of nitric acid near 1700 cm−1

The infrared spectrum of the ν₂ band of nitric acid (HNO₃) has been measured with a tunable diode laser in the frequency interval from 1690 to 1727 cm^?1. A total of 430 assigned transitions have been analyzed to yield a set of nine rovibrational constants for the upper state with a standard deviation of 0.0012 cm^?1. The band is primarily B type with a band center at 1709.568 ± 0.005 cm^?1. Because of the absence of perturbations, the band constants can be used to calculate transition frequencies and relative intensities with a high degree of accuracy.     

Absolute intensity measurements of the CO2 bands 401III←000 and 411III←010

The absolute intensities of the transitions 401_III←000 and 411_III←010 of CO₂ have been measured from spectra obtained under high resolution. Both the vibration-rotation line intensities and the integrated band intensities are reported. The rotationless transition moment of 401_III←000 is deduced and a vibration-rotation interaction factor F(m) = 1+(4.92×10^?4)m+(4.4×10^?7)m² is determined. The values obtained are: S_Band(401_III←000) = (25.54±0.22)×10^?5 cm^?2atm_{(293 K)}^?1, |R₀₀₀^401_III| = (1.87±0.02)×10^?4D, and S_Band(411_III←010) = (1.83±0.13)×10^?5 cm^?2atm_{(293 K)}^?1.     

A simultaneous analysis of the microwave,submillimeterwave, far infrared,and infrared-microwave two-photon transitions between the ground and ν2 inversion-rotation levels of 14NH3

Fourier transform infrared spectra of the inversion-rotation transitions have been measured with 0.010-cm^?1 resolution between 40 and 300 cm^?1 in the ground state and ν₂ excited states of ¹⁴NH₃. Submillimeterwave spectra of the inversion and inversion-rotation transitions in the ν₂ state of ¹⁴NH₃, including a few Δk = ±3 “perturbation-allowed” transitions, have been measured with microwave accuracy between 540 and 770 GHz. A simultaneous least-squares analysis of these data, the microwave ground-state transition frequencies, and the ν₂ infrared-microwave two-photon transition frequencies has been carried out. A theory of the Δk = ±3n interactions in the ground and ν₂ excited states of ammonia (S. P. Belov, L. I. Gershtein, A. F. Krupnov, A. V. Maslovskij, ?. Urban, V. ?pirko, and D. Papou?ek, J. Mol. Spectrosc.84, 288–304 (1980)) has been used in the analysis. A set of the ground- and ν₂-state molecular parameters has been obtained which describes the experimental data within the precision of the experiment. The “smoothed” values of transition frequencies can be used for calibration purposes with a precision better than 3 × 10^?5 cm^?1 in the submillimeterwave region, better than 10^?3 cm^?1 in the far-infrared region, and better than 1.5 × 10^?3 cm^?1 in the region 700 – 1200 cm^?1.     

Nonlinear laser UV photochemistry of maleic acid in aqueous solution

This work deals with photochemical transformations of maleic acid in an aqueous solution under powerful picosecond fourth-harmonic pulses of a YAG-Nd³⁺ laser with λ=266 nm and nanosecond pulses of an excimer KrF laser with λ-248 nm. It has been found that by changing the irradiation intensity only it is possible to produce selectively different products with a high quantum yield resulting from the following reactions of the ?C=C? bond of the maleic acid molecule: 1) cis-trans isomerization at radiation intensities up to 10⁸ W/cm² as a result of linear photochemistry; 2) radical dimerization of the maleic acid withJ=10⁸÷10⁹ W/cm² and water addition to the ?C=C? bond of the maleic acid withJ?10⁹ W/cm² as a result of nonlinear photochemistry.     

Absorption spectra of Cu2+ in azurite

EPR and optical absorption studies in azurite have been carried out at room and low temperatures. The EPR spectrum reveals that the ground state for Cu²⁺ ion is ²B₁. Peak to peak linewidth of EPR spectrum is calculated (ΔH_p = 76 G) and found to be close with the observed value. The Cu²⁺ ion situated in D_4h symmetry with spin-orbit interaction exhibits bands at 11,806, 16,484, 17,952 and 19,793 cm^?1. The tetragonal field parameters are calculated to be Ds = ? 3364 cm^?1 and Dt = ? 604 cm^?1. The crystal field splitting parameter is found to be Dq = ? 1175 cm^?1.     

Superradiation from non-ideal plasmas in electric field

An effect of external static electric field on emission of radiation from non-ideal plasmas of erosion focus has been experimentally observed. An order-of-magnitude increase in radiation intensity for spectral interval hv = 40 ? 350 eV with electric field increasing up to 10³V/cm has been found for plasmas with $\text{ξ}\text{Z}\text{?1}$, where ξ is the number of electrons in Debye sphere, Z = 2 ? 3 is the stage of ionization. The energy emitted has been several times higher than the black body energy for the same spectral interval at maximum electric field achieved. The effect vanishes at $\text{ξ}\text{Z}\text{?10}$.     

The infrared spectrum of OH-compensated defect sites in C-doped MgO and CaO single crystals

The IR spectra of OH-compensated point defects in MgO (and CaO) single crystals of various purity grades were reinvestigated. Three distinct groups of IR bands appear in the O-H stretching region: A, B and C around 3550 cm^?1 (3650 cm^?1), 3300 cm^?1 (3450 cm^?1) and 3700cm^?1 (3750cm^?1). They are assigned as follows: band A to the fully compensated, band B to the half compensated and band C to the overcompensated cation vacancies, [O?V”_catH?]^×, [O?V”_cat], and [O?O?V”_catH?$\text{]}\text{?}$, respectively.Upon cooling to 80 K the band A shows a complex behavior partly due to the formation of Ha molecules by charge transfer and concommittant O^? formation: [? (H₂)”_cat?]^×. The O^? represent defect electrons or positive holes in the O^2? matrix.Bands A and B show a characteristic multiplet splitting which is caused by local lattice strains coming from carbon atoms on near-by interstitial position. The intensity ratios between the multiplet components remain constant regardless of temperature pretreatments up to 1470 K, but strong variations of the integral intensities are observed. These are caused by the highly mobile C atoms entering and leaving reversibly the cation vacancy sites as a function of temperature and of the quenching speed. When the C atoms push the H₂ molecules onto interstitial sites, an H-H stretching signal appears around 4150cm^?1.     

Dielectric behaviour of cellulose acetate-based polymer electrolytes

The present work deals with the findings on the dielectric behaviour of cellulose acetate (CA) and its complexes consisting of ammonium tetrafluoroborate (NH₄BF₄) and polyethylene glycol with a molecular weight of 600?g/mol (PEG₆₀₀) that were prepared using the solution casting method. The highest ?? obtained for CA-NH₄BF₄ film was 2.18?×?10^?7 S cm^?1 and enhanced to 1.41?×?10^?5 S cm^?1 with the addition of 30?wt.% PEG₆₀₀. The dielectric behaviours of the selected samples were analyzed using complex impedance Z*, complex admittance A*, complex permittivity ?*, and complex electric modulus M*-based frequency and temperature dependence in the range of 10?Hz?C1?MHz and 303?C363?K, respectively. The variation in dielectric permittivity (?? _r and ?? _i) as a function of frequency at different temperatures exhibits a dispersive behaviour at low frequencies and decays at higher frequencies. The variation in dielectric permittivity as a function of temperature at different frequencies is typical of polar dielectrics in which the orientation of dipoles is facilitated with the rising temperature, and thereby the permittivity is increased. Modulus analysis was also performed to understand the mechanism of electrical transport process, whereas relaxation time was determined from the variation in loss tangent with temperature at different frequencies.     

Raman-brillouin light scattering determination of the structural correlation range in ges2 glass

Polarized Brillouin and low frequency (3 cm^?1 ? ω ? 40 cm^?1) Raman spectra of GeS₂ glass have been measured. Parameters determined from the Brillouin spectra have been used in the theory of Martin and Brenig to obtain from a fit of the Raman spectrum the structural correlation range, 2σ. We find 2σ = 8 ± 1 Å.     

Microspectral analysis of dentine with femtosecond laser induced plasma

Microspectral analysis of dentine plasma produced by femtosecond laser radiation with intensities of I ～ 10¹³?10¹⁵ W/cm² in ambient atmosphere has been measured. C, O, Ca, Zn, Na, and Cu spectral lines were identified. The X-ray radiation with energies E > 30 keV has been observed upon laser beam intensities of I ～ 5 × 10¹⁵ W/cm².     

Measurements of the HCN ν3 band broadened by N2

N₂-broadened halfwidths have been measured for 51 absorption lines belonging to the ν₃ fundamental band of hydrogen cyanide (¹H¹²C¹⁴N) near 3311 cm^?1. The data were recorded at room temperature using a Fourier transform spectrometer with a nominal resolution of 0.06 cm^?1. A nonlinear least-squares spectral-fitting procedure was used to obtain both line intensities and collision-broadened halfwidths from scans recorded at several different pressures. The N₂-broadened halfwidths, determined for all lines with J ≤ 25 in both the P and R branches of the band, show the expected distribution with J for broadening by a nonpolar gas. The halfwidth values range from approximately 0.17 cm^?1 atm^?1 near the band center to 0.11 cm^?1 atm^?1 for high-J lines. The band intensity for the ν₃ fundamental derived from these measurements is 236.2 ± 9.5 cm^?2 atm^?1 at 296 K, and empirical coefficients for the vibration-rotation interaction F-factor were also determined.     

Relative intensities in X-ray photoelectron spectra

An experimental determination of the relative intensities of X-ray photoelectron lines corresponding to the inner levels of elements with Z ? 20, and calculations of the total photo-ionization cross-sections for all shells of these elements with the Hartree—Fock—Slater potential are reported. The experimental and theoretical values agree well for the 1s levels while marked discrepancies are revealed for the 2p levels. The theoretical values of the cross sections for the atomic valence levels are used to calculate the relative intensities of molecular levels in CF₄, BF₄^?, BeF₄^2?, LiF, NO₃^?, CO₃^2?, CO, N₂, CO₂, H₂O and C₄H₅N. The results of the calculations agree satisfactorily with experiment.     

Relative intensities in x-ray photoelectron spectra

An experimental determination of the relative intensities of X-ray photoelectron lines corresponding to the inner levels of elements with Z ? 20, and calculations of the total photo-ionization cross-sections for all shells of these elements with the Hartree—Fock—Slater potential are reported. The experimental and theoretical values agree well for the 1s levels while marked discrepancies are revealed for the 2p levels. The theoretical values of the cross sections for the atomic valence levels are used to calculate the relative intensities of molecular levels in CF₄, BF₄^?, BeF₄^2?, LiF, NO₃^?, CO₃^2?, CO, N₂, CO₂, H₂O and C₄H₅N. The results of the calculations agree satisfactorily with experiment.