A collisional cooling investigation of the pressure broadening of the 110←101 transition of water from 17 to 200 K

An investigation of the 1₁₀←1₀₁ rotational transition of water at 556 GHz pressure broadened by hydrogen, helium, nitrogen, oxygen and carbon dioxide has been completed. Using the collisional cooling technique the broadening of this transition by each gas was explored from 200 K down to the condensation point of the broadening gas or 17 K, which ever is lower. This marks the first time such an extensive investigation of the broadening of this rotational transition as a function of temperature has been completed. The results of this investigation will be presented including the exponential temperature dependence of the broadening, the lack of temperature dependence of the broadening observed in helium and the unique behavior of the hydrogen broadening at low temperature (<40 K). In addition, the broadening of the 1₁₀←1₀₁ rotational transition of water by nitrogen and oxygen was recorded at room temperature and a direct comparison of this data with recent work will be discussed.     

Pressure broadening of the ground vibrational state J = 31→J = 32 transition of CH3F by coincidence laser spectroscopy

We have studied self-broadening and foreign gas broadening of the ground state J = 31→J = 32 transition of CH₃F using a coincidence with the 184.3 μm emission from an optically pumped CH₂F₂ laser. Experiments have been carried out with polar and non-polar species as well as the noble gases.This transition is in the region where the classical rotation period is of the same order as the duration of a collision. The measurements indicate an anomalously low value of 7.0 MHz/Torr for the self-broadening coefficient of CH₃F and an unusually large value for the CH₃OH broadening coefficient. The latter is believed to be due to the presence of a low energy OH torsional model in CH₃OH.     

Synthesis,Structure, and Thermophysical Properties of Pb10 – xBix(GeO4)2 + xVO4)4 – x (x = 0–3) in the Temperature Range of 350–950 K

Physics of the Solid State - The Pb10&nbsp;–&nbsp;xBix(GeO4)2&nbsp;+&nbsp;x(VO4)4&nbsp;–&nbsp;x (x = 0–3) compounds with an apatite structure have been...     

Pressure broadening coefficients of transitions in the ν5 band of methyl bromide from fitting to Voigt and Galatry line profiles

Tuneable diode laser absorption spectroscopy has been used to measure the room temperature pressure broadening coefficients (γ) of rotational transitions in the v₅ fundamental band of methyl bromide (¹²CH₃⁷⁹Br and ¹²CH₃⁸¹Br) around 6.9 μm. Nitrogen, oxygen and self-broadening coefficients have been determined for 125 lines in the ^RQ₁, ^PQ₃, ^PQ₅, ^PQ₇ and ^PQ₈ branches and 49 P and R branch transitions. Line profiles within Q branches were recorded at incremental pressures of nitrogen and oxygen up to 15 Torr and fitted to a Voigt profile to yield the broadening coefficients. The nitrogen broadened data for 14 lines, chosen from the five Q branches, were also fitted with Galatry profiles. The line profiles of the P and R branch transitions were recorded for total nitrogen and oxygen pressures of up to 300 Torr and fitted to both Voigt and Galatry profiles. Within individual Q branches, nitrogen broadening coefficients were found to decrease monotonically with increasing J from 0.14 cm⁻¹ atm⁻¹ at low J to 0.09 cm⁻¹ atm⁻¹ at high J. The corresponding values for oxygen were approximately 25% smaller. Self-broadening coefficients were found to vary between 0.48 and 0.16 cm⁻¹ atm⁻¹ with a similar J dependence to the foreign gas broadening for J > 20. However, between J = 2 and J ≈ 20 the broadening coefficient was found to increase with J. The magnitude of the pressure broadening coefficient for P and R branch transitions was found to closely follow the J dependence measured for the Q branch lines.     

A Role of the 3d Electron Subsystem in the Evolution of Band Structure and Magnetic and Optical Properties of ErNi5 – xCox Compounds (x = 0–4)

Physics of the Solid State - The evolution of the electronic structure and optical and magnetic properties of ErNi5&nbsp;–&nbsp;xCox compounds (x = 0–4), occurring upon...     

A thermoluminescence study of mineral silicates extracted from herbs in the dose range 0.5–5 Gy

The presence of silicates in many personal objects suggests their potential use at low dose as fortuitous dosimeter in an accidental radiological exposure, when conventional dosimetry is not available. The goal of the present work is the dosimetric characterization of mineral silicates extracted from the plant Hibiscus Sabdariffa L, known as Jamaica flower, in the dose range 0.5–5 Gy. By studying the radiation-induced signal in time, the temperature integration region between 210 °C and 250 °C was found to be the most stable and also reduced the effects of thermal fading in the dose reconstruction process; the dose response curve was linear between 0.5 Gy and 5 Gy. By checking the change in sensitivity after repeated exposures to ionizing radiations and to high temperature heating, no variation in the glow curve shape or peak intensities were detected. To eliminate a pre-existing background signal, all the characterization measurements were performed with aliquots “annealed” by a preliminary readout of the TL.     

Pressure broadening parameters of the hydroxyl radical A 2 Σ+ (υ’=0) ← X 2 Π3/2 (υ=0) transitions at ca. 308 nm

Pressure broadening widths and pressure-induced frequency shifts for the hydroxyl radical Q11([see full textsee full text]), Q21([see full textsee full text]), Q11(2), Q21(2) absorption lines in the A band at ca. 308 nm have been determined in the presence of a variety of gases (N2, Ar, Ne and He). Hydroxyl radicals were formed using either a microwave discharge or a vacuum ultra-violet photolysis of water vapour and were detected using direct absorption spectroscopy with a bandwidth normalised noise equivalent absorption sensitivity of 5 ×10-5 Hz-1/2. A tunable external cavity diode laser at 835 nm and a single-frequency continuous-wave intracavity frequency-doubled diode laser at 488 nm were used to produce tunable continuous-wave light at 308 nm by sum-frequency generation in a -BaB2O4 crystal.     

Atomic structure of the (3 × 2) Si–GaAs (0 0 1) reconstructed surface: A clue to δ doping mechanism derived from in situ grazing incidence X-ray diffraction data

In view of understanding silicon incorporation in the δ doping process of GaAs (0 0 1), Si atoms have been deposited, under UHV, on a α(2 × 4) arsenic terminated substrate. In the low coverage regime, a transition to a less As rich (3 × 2) reconstructed Si–GaAs (0 0 1) surface was observed whose atomic structure has been investigated by grazing incidence X-ray diffraction performed in situ. Silicon is found to occupy not only a Ga substitutional site, precursor of a donor dopant but also to form nuclei for neutral clusters, on a template made by the (3 × 2) GaAs (0 0 1) reconstructed surface observed by Martrou et al. [Phys. Rev. B 72 (2005) 241307®]. The maximum surface concentration of donor-like silicon is estimated at 1.04 × 10¹⁴ cm^?2 (1/6th monolayer).     

Observation of forbidden transitions in the ν4 band of NH3: corrections to the ground state ΔK = 3 intervals

This paper presents a preliminary evaluation of the C rotational constant and coefficients of the operators P_z ²ⁿ up to n = 4 for NH₃ in the ground state. These constants are evaluated on the basis of the determination of 14 different ΔK = 3 ground state intervals obtained from measurement of many Δ(K - l) = 3 transitions observed in the ν₄ vibration rotation band. Corrections to the ground state term values for NH₃ are given as a function of K, thus permitting ΔK = 3 transitions to be determined with accuracies comparable to those of normal allowed transitions. The perturbation which gives rise to the observed transitions is large, but has not been treated in previous analyses of the ν₄-2ν₂ bands.     

Diffusion of a Ga adatom on the GaAs(001)‐c(4 × 4)‐heterodimer surface: A first principles study

The adsorption and diffusion behavior of a Ga adatom on the GaAs (001)‐c(4 × 4)-heterodimer surface were studied by employing ab initio density functional theory (DFT) computations in the local density approximation. Structural and bonding features of the c(4 × 4)-heterodimer reconstruction surface were examined. A comparison with the c(4 × 4)-ss reconstruction was performed. Minimum energy sites (MES) on the c(4 × 4)-heterodimer surface were located by mapping the potential energy surface for a Ga adatom. Barriers for diffusion of a Ga adatom between the neighboring MES were calculated by using top hopping- and exchange-diffusion mechanisms. We proposed two unique diffusion pathways for a Ga adatom diffusing between the global minimums of two neighboring unit cells. Signature differences between electronic structures of top hopping- and exchange‐diffusion mechanisms were studied for relevant atoms. We observed a higher diffusion barrier for exchange mechanism compared to top hopping.     

Anomalous charge transfer in La<Subscript>2</Subscript>CuO<Subscript>4</Subscript> near the Néel temperature: Evidence of the transition from spin liquid to two-sublattice antiferromagnetic state

The temperature dependence of the electrical resistance and thermopower of La_{2? x}Sr_xCuO_4+δ single crystals with x ? 0.003 and δ<0.05 has been studied in the temperature range from 100 to 400 K. All crystals exhibiting two-dimensional hopping conductivity via neighboring acceptor sites in the CuO₂ plane show a significant difference in the charge transfer below and above the Néel temperature T_N. This difference indicates that the loss of a two-sublattice antiferromagnetic order strongly affects the charge transport in the CuO₂ plane. The obtained data lead to a conclusion that the crystal above T_N occurs in a resonance valence bond state of the Bose type.     

Near-threshold photoionization from the excited mp<Superscript>5</Superscript>(m + 1)p J = 0−3 levels of Ar,Kr and Xe (m = 3−5)

Using the configuration interaction Pauli-Fock including core polarization (CIPFCP) approach we have calculated absolute total and partial cross sections for photoionization of excited mp ⁵(m + 1)p J = 0−3 levels in Ar, Kr and Xe (m = 3−5) near threshold. Particular emphasis is paid to the lineshapes of the odd mp _1/2⁵ n(s/d)′ autoionizing resonances and their variation with the character of the intermediate excited J = 0−3 state. For selected intermediate levels of Ar and Kr the computed cross sections are compared with laser spectroscopic measurements; good agreement between the theoretical and experimental lineshapes and branching ratios for different resonances is observed.     

The infrared spectrum of 12C2HD: the bending states up to υ4 +υ5 =3

The infrared spectrum of ¹²C₂HD has been recorded at high resolution between 450 and 2100?cm^?1 by Fourier transform spectroscopy. The ν₄ and ν₅ bending fundamental bands together with overtones, combination bands and associated hot bands involving modes up to υ_tot?=?υ₄?+?υ₅?=?3 have been identified. Altogether, 43 vibrational bands have been analysed, leading to the spectroscopic characterization of the ground state and of 18 vibrationally excited states. They include all the components of the vibrational manifolds up to υ_tot?=?3, with the exception of the υ₄?=?3, ??=?±3 state. A simultaneous fit of all the assigned transitions has been performed. The adopted model includes vibration and rotation ?-type interaction resonances. The determined spectroscopic parameters reproduce the assigned wavenumber transitions with RMS values close to the estimated experimental uncertainties.     

Ordered structure of the directions of arrival of E<Subscript>0</Subscript>∼5×10<Superscript>17</Superscript> eV cosmic rays according to data from the Yakutsk array for recording extensive air showers

Results are presented that were obtained by analyzing arrival directions for cosmic rays recorded by the Yakutsk array between 1974 and 2001 in the energy range E₀=10^17.6–17.9 eV for zenith angles in the region θ≤53°. It is shown that their flux consists of two components—an isotropic (about 75%) and a cluster (about 25%) one—that are characterized by sharply different degrees of anisotropy. At E₀=10^17.7–17.8 eV, the observed showers are found to be strongly correlated with the Supergalaxy plane.     

Gas chromatography coupled to mass spectrometry-based metabolomic to screen for anabolic practices in cattle: identification of 5α-androst-2-en-17-one as new biomarker of 4-androstenedione misuse

The use of anabolic steroids as growth promoters for meat-producing animals is banned within the European Union. However, screening for the illegal use of natural steroid hormones still represents a difficult challenge because of the high interindividual and physiological variability of the endogenous concentration levels in animals. In this context, the development of untargeted profiling approaches for identifying new relevant biomarkers of exposure and/or effect has been emerging for a couple of years. The present study deals with an untargeted metabolomics approach on the basis of GC-MS aiming to reveal potential biomarkers signing a fraudulent administration of 4-androstenedione (AED), an anabolic androgenic steroid chosen as template. After a sample preparation based on microextraction by packed sorbent, urinary profiles of the free and deglucurono-conjugates urinary metabolites were acquired by GC-MS in the full-scan acquisition mode. Data processing and chemometric procedures highlighted 125 ions, allowing discrimination between samples collected before and after an administration of 4-AED. After a first evaluation of the signal robustness using additional and independent non-compliant samples, 17 steroid-like metabolites were pointed out as relevant candidate biomarkers. All these metabolites were then monitored using a targeted GC-MS/MS method for an additional assessment of their capacity to be used as biomarkers. Finally, two steroids, namely 5α-androstane-3β,17α-diol and 5α-androst-2-en-17-one, were concluded to be compatible with such a definition and which could be finally usable for screening purpose of AED abuse in cattle.