The absorption line profiles of H2O near 1.39 μm in binary mixtures with N2, O2, and H2 at low pressures

The absorption line profiles of water vapor in binary mixtures with diatomic molecules H₂, N₂, and O₂ have been recorded on a diode laser spectrometer. The profiles of several lines of the 101 band have been studied near 1.39 μm with a spectral resolution of 3 × 10^?4 cm^?1. The pressure of the binary mixtures was varied from 0 to 200 Torr. The experimental data obtained have been used to test the Voigt, Rautian-Sobel’man, and Galatry theoretical models of a spectral line profile. The coefficients of collisional narrowing have been determined from the results of the fitting.     

High resolution polarization spectroscopy and laser induced fluorescence of CO<Subscript>2</Subscript> around 2μm

High resolution Infrared Polarisation Spectroscopy (IRPS) and Infrared Laser Induced Fluorescence (IRLIF) techniques were used to probe CO₂/N₂ binary gas mixture at atmospheric pressure and ambient temperature. The probed CO₂ molecules were prepared by laser excitation to an overtone and combination ro-vibrational state (12⁰1, J=15) of CO₂, centred at 4988.6612 cm^-1. IRPS and IRLIF line profiles were recorded for several CO₂/N₂ binary mixtures. The observed IRLIF line shapes have the expected Lorentzian form while the observed IRPS line shapes are narrower by a factor of two than those recorded with the IRLIF and appear to have a Lorentzian-cubed profile. The recorded line profiles provide measurements of the pressure-broadening coefficient directly at atmospheric pressure. The Full-Width-Half-Maxima (FWHM) pressure broadening coefficients are measured, based on IRLIF, to be 0.2174±0.0092 cm^-1atm^-1 and 0.1327 ±0.0077 cm^-1atm^-1 for self- and N₂ collision broadening, respectively. The broadening coefficients obtained based on IRPS were measured to be ~8% larger than those obtained with IRLIF.     

Electronic density distorsion of NiO2 due to intercalation by Li

High resolution measurements of Compton profiles of Li_xNiO₂ have been carried out using 60 keV photons at ESRF (Grenoble, France). Theoretical profiles are obtained using the plane wave expansion of wave functions calculated using ab-initio SCF method. Theory and experiment are in good agreement. We have further decomposed the charge density modification into a rigid charge transfer from lithium to e_g¹ states of NiO₂ and the distorsion of NiO₂ charge density mainly due to Ni–O bond changes resulting from lattice parameter change and Jahn-Teller effect.     

Tunable diode laser spectroscopy of CO2 in the 10- to 15-μm spectral region—Lineshape and Q-branch head absorption profile

The self-broadened and nitrogen-broadened absorption profiles of the Q-branch head of the 10⁰0 ← 01¹0 band of CO₂ near 618 cm^?1 were studied under high resolution (～10^?4 cm^?1) using tunable diode laser techniques. The intensity and linewidth of several lines in this Q branch, the ν₂ band, 10.4-μm and 9.4-μm laser bands have been measured accurately. The lineshape of a CO₂ line has also been measured to be Lorentzian within experimental accuracy to about 15 half-widths. Preliminary calculated Q-branch head absorption profiles agree reasonably well with the observed profiles.     

Characterization of laser-induced plasma plume: Comparison between Al and Al2O3 targets

Characterization of the plasma plume produced by laser ablation from Al and Al₂O₃ targets was carried out on the basis of the line profile analysis of Al(I) (²P°–²S) emission. The spatial distribution and density parameters of electrons and Al atoms in the plume were obtained by comparing observed spectral line profiles with a theoretical calculation. The results showed different behavior for the Al and Al₂O₃ targets. The Al atoms from the Al₂O₃ target were populated in a smaller region than those from the Al target. PACS 52.38.MF; 52.70.Kz; 52.25.Os     

Raman scattering in K2Pt(CN)4Br0.3 · 3H2O

Raman scattering experiments on K₂Pt(CN)₄Br_0.3 · 3H₂O are reported between 5 and 300 K as a function of temperature. A line of A₁ symmetry detected at 44 cm^?1 shows interesting temperature dependent properties. It is concluded from a comparison of the frequency, symmetry, and scattering intensity of this line with theoretical predictions that the excitation concerned represents the amplitude mode of the charge density wave (the line observed in infrared absorption being the phase mode). No Peierls transition is observed, but the results are consistent with a Peierls distortion present at all temperatures. The findings are correlated with inelastic neutron scattering and infrared studies. Finally, the CN stretching modes at 2189 and 2173 cm^?1 and the water mode at 3490 cm^?1 are studied as a function of temperature.     

Determination de la densite electronique d'un plasma ionise a partir de la distance entre les pics de la raie ‘permise’ LiI et de la raie ‘interdite’ LiI

The aim of this investigation is to verify the method of measuring electron concentrations in partially ionized plasmas on the basis of a comparison of an ‘allowed’ line [such as the LiI (2s² 2p ²P−2s² 4f ²D) line] and a ‘forbidden’ neighbouring line induced by the ionic field [such as the LiI (2s² 2p ²P−2s² 4f ²F) line]. First, the line profiles are calculated theoretically. They are then compared with the observed profiles. It is found that the separation Δ(N_e) between the intensity maxima of the two lines may be conveniently used for the evaluation of the electron concentration N_e. This method is more convenient than one based on the measurement of the width of the ‘allowed’ line or on measurement of the maximum intensity ratios of the ‘allowed’ and ‘forbidden’ lines.     

Effects of humidified atmosphere on oxygen transport properties in La2Mo2O9

The effects of humidified atmosphere on oxygen surface exchange and diffusion in La₂Mo₂O₉ have been investigated. After annealing samples in D₂O vapour, the depth and line scan profiles of the OD^- species showed the incorporation of hydroxyl groups on the surface and of diffusion into the bulk. The hydroxyl diffusion process appears to be different from that of oxygen diffusion, and might indicate the existence of ambipolar diffusion of oxide ions and hydroxyl species in La₂Mo₂O₉.     

NMRON studies of the quasi-2-dimensional ferromagnet 54Mn-Mn(COOCH3)2·4H2O

Pulsed and continuous wave NMRON, and NMR thermally detected by Nuclear Orientation have been used to investigate the magnetic properties of the quasi-2-dimensional ferromagnet ⁵⁴Mn-Mn(COOCH₃)·4H₂O. The NMR frequencies of both the ⁵⁴Mn spins and the abundant ⁵⁵Mn spins have been determined for the two crystalline lattice sites Mn1 and Mn2. The line widths of the ⁵⁴Mn resonances are homogeneously broadened to about 300 kHz, and the ⁵⁵Mn resonances are significantly pulled down in frequency. The spin-lattice relaxation times in low applied magnetic fields are short with T₁ for the Mn2 site being much less than the value for the Mn1 site. Level crossing is observed between the Mn1 and Mn2 resonances in an applied field of 2.6 T. This revised version was published online in August 2006 with corrections to the Cover Date.     

Suppression of the charge density waves in 1T-TaS2 by 70 MeV16O6+ bombardment

We report on the measurement of the nuclear quadrupole interaction by TDPAC on a single crystal of 1T-TaS₂ before and after bombardment with 70 MeV¹⁶O⁶⁺ ions. In 1T-TaS₂, two groups of inequivalent Ta-sites are observed at 298 K due to the presence of a nearly commensurate charge density wave (CDW) Upon¹⁶O⁶⁺ bombardment a single slightly broadened line is observed which resembles closely the incommensurate CDW state.     

Stark broadening of isolated lines: calculation of the diagonal multiplet factor for complex configurations (n1l1 n n2l2 m n3l3 p)

Owing to the increasing sensitivity of detectors, accurate line profiles are needed for accurate stellar atmospheres modelling and for laboratory and technological plasmas as well. So, Stark broadening parameters of isolated lines of complex atoms and ions within the impact and quasistatic approximation are needed, even if the atomic abundance of the considered element is low. Angular factors of the diagonal line strength entering the quadrupole term appearing in the semi-classical expression of the width of line broadened by electron or ion perturbers, are needed. The aim of this paper is to extend the previous calculations of this diagonal multiplet factor which were obtained for configurations of the type lⁿ and l₁ ⁿl₂ ^m to more complex configurations in LS coupling. To study the Stark broadening of isolated lines in the impact and quasistatic approximation, we use the semi-classical-perturbation treatment, including both dipole and quadrupole contribution in the expansion of the electrostatic interaction between the optical electron and the perturber. We also use the Fano-Racah algebra. Angular factors of the diagonal line strength entering the quadrupole term appearing in the semi-classical expression of the width of line broadened by electron or ion perturbers, are calculated. New diagonal multiplet factor formulae for more complicated configurations such as (n₁l₁ ⁿ(L_nS_n)n₂l₂ ^m(L_mS_m)n₃l₃ ^p(L_pS_p)) are provided. These formulae can enter the computer Stark semi-classical perturbation codes.     

An empirical study on the importance of a speed-dependent Voigt line shape model for tropospheric water vapor profile remote sensing

We use high quality ground-based solar absorption spectra measured in close coincidence with Vaisala RS92 radiosonde in situ water vapor profiles to demonstrate that a Voigt line shape model yields systematic errors in the remotely sensed tropospheric water vapor profiles. We analyse absorption signatures of 4 H₂¹⁶O and 2 HD¹⁶O bands situated between 790 and 4710 cm⁻¹. We find that applying a speed-dependent Voigt line shape model instead of a Voigt line shape model significantly improves the agreement between the water vapor profiles obtained by the radiosondes and by infrared remote-sensing in the different bands. An optimal agreement is obtained for a Γ₂ (relaxation rate for speed-dependence) of 6-21% of Γ₀ (Voigt relaxation rate), which is consistent to the values derived from laboratory experiments. Our study suggests that further extensive laboratory investigations of line shape models are a key for improving the quality of modern water vapor remote sensing products.     

N2- and O2-broadening of CO2 for the (301)III ← (000) band at 6231 cm

The N₂- and O₂-broadening effect have been investigated for 10 absorption lines of the CO₂ (30⁰1)_III ← (00⁰0) band centered at 6231 cm⁻¹, in the range from P(28) to R(28) by a near-infrared diode-laser spectrometer. We have analyzed the observed line profiles with the Galatry function, and determined the N₂- and O₂-broadening coefficients precisely. The air-broadening coefficients for these lines have been derived. The present results are compared with those of the previous studies for this band and with some of the other bands.     

Absolute line wavenumbers in the near infrared: 12C2H2 and 12C16O2

40 absolute line wavenumbers in the 3v ₃ band of ¹²C¹⁶O₂ between 6927 cm^?1 and 6989 cm^?1 and 626 absolute line wavenumbers in the near infrared absorption spectrum of ¹²C₂H₂ between 7060 cm^?1 and 9900 cm^?1 have been measured using high resolution Fourier transform spectroscopy. The calibration of the CO₂ line wavenumbers relied on heterodyne frequencies available in the v ₁ + v ₃ band of ¹²C₂H₂ near 6556 cm^?1. The absolute uncertainty of the calibrated CO₂ line wavenumbers is estimated to 0.000 08 cm^?1. The acetylene spectra were calibrated using heterodyne frequencies available in the 2—0 band of ¹²C¹⁶O and the line wavenumbers obtained in the 3v ₃ band of ¹²C¹⁶O₂. The absolute uncertainty of the calibrated acetylene line wavenumbers is estimated to range from 0.0003 cm^?1 to 0.006 cm^?1 for strong to very weak isolated lines. Comparison with absolute line wavenumbers obtained independently at JPL in the 3v ₃ band of ¹²C₂H₂ near 9649 cm^?1, calibrated using absolute wavenumbers available in the 2—0 and 3—0 (near 6350 cm^?1) bands of ¹²C¹⁶O, shows very good agreement. Also, the vibration—rotation constants for the observed upper vibrational states of ¹²C₂H₂ were determined, but without accounting for the perturbations affecting these states.     

Magnetism and superconductivity in (RE) Ni2B2C: The case of TmNi2B2C

The recently reported coexistence of an oscillatory magnetic order with wave vector Q = 0.241⁻¹ and superconductivity in TmNi₂B₂C is analyzed theoretically. It is shown that the oscillatory magnetic order and superconductivity interact predominantly via the exchange interaction between localized moments (LMs) and conduction electrons, while the electromagnetic interaction between them is negligible. In the coexistence phase of the clean TmNi₂B₂C the quasiparticle spectrum should have a line of zeros at the Fermi surface, giving rise to the power-law behavior of thermodynamic and transport properties. Two scenarios of the origin of the oscillatory magnetic order in TmNi₂B₂C are analyzed: (a) due to superconductivity and (b) independently of superconductivity. Experiments in a magnetic field are proposed in order to choose between them.     

Analytical approximations for speed-dependent spectral line profiles

Analytical approximate expressions for speed-dependent Rautian-Sobel'man, Voigt, and general line profiles, including spectral line mixing, were obtained. Systematic errors of the approximate profiles are within 0.7% for the mass ratios of perturbing and absorbing molecules m_b/m_a≤9. The calculation time of the approximate line profiles is much shorter than the time required for calculating exact expressions for the line profiles. An approximate analytical expression for the observable homogeneous line width was derived. A least-square fitting of the singlet methane absorption line centered at 6107.17 cm⁻¹ was performed, using the approximate line profiles obtained.     

TDLAS-based in situ measurement of absolute acetylene concentrations in laminar 2D diffusion flames

We report the first quantitative and calibration-free in situ C₂H₂ measurement in a flame environment using direct Tunable Diode Laser Absorption Spectroscopy(TDLAS). Utilizing a fiber-coupled Distributed Feedback diode laser near 1535 nm we measured spatially resolved, absolute C₂H₂ concentration profiles in a laminar non-premixed CH₄/air flame supported on a modified Wolfhard-Parker slot burner with N₂ purge slots to minimize end flames. We developed a wavelength tuning scheme combining laser temperature and current modulation to record with a single diode laser a mesh of 37 overlapping spectral windows and generate an ∼7 nm (30 cm⁻¹) wide, high-resolution absorption spectrum centered at 1538 nm. Experimental C₂H₂ spectra in a reference cell showed excellent agreement with simulations using HITRAN2004 data. The enhanced wavelength coverage was needed to establish correct C₂H₂ line identification and selection in the very congested high temperature flame spectra and led to the P17e line as the only candidate for in situ detection of C₂H₂ in the flame. We used highly efficient optical disturbance correction algorithms for treating transmission and background emission fluctuations in combination with a multiple Voigt line Levenberg-Marquardt fitting algorithm and Pt/Rh thermocouple measurements to achieve fractional optical resolutions of up to 4 × 10⁻⁵ OD (1σ) in the flame (T up to 2000 K). Temperature dependent C₂H₂ detection limits for the P17e line were 60 to 480 ppm. By translating the burner through the laser beam with a DC motor we obtained spatially resolved, absolute C₂H₂ concentration profiles along the flame sheet with 0.5 mm spatial resolution as measured with a knife edge technique. The TDLAS-based, transverse C₂H₂ concentration profiles without any scaling are in excellent agreement with published mass spectrometric C₂H₂ data for the same flame supported on a similar burner, thus validating our calibration-free TDLAS measurements.     

Absorption profiles of HCl for the J = 1-0 rotational transition: Foreign-gas effects measured for N2, O2, and Ar

Line profiles of the J = 1-0 transition of the hydrogen chloride, H³⁵Cl and H³⁷Cl isotopomers, were measured with a BWO-based submillimeter-wave spectrometer at AIST in real form: three hyperfine transitions for each isotopomer, i.e., total six lines at 625 and 626 GHz. The effect of foreign gases on the broadening and shift was determined for N₂, O₂, and Ar. The modified Voigt function was applied as the line shape function for preliminary analysis, where the collisional-narrowing effect was clearly observed. In the final analysis, we applied the Galatry function and determined the integral intensity, line center position, Lorentzian width, and contraction parameter for each absorption line. The magnitudes of the foreign-gas pressure-broadening coefficients decrease in order of N₂, O₂, and Ar. The line-shift coefficients were clearly observed, the magnitudes of which decrease in order of Ar, O₂, and N₂. The pressure dependence of contraction parameter was determined, although with poor precision.     

Thermal expansion of lT-TaS2 and 2H-NbSe2

The thermal expansion of the a and c axes of lT-TaS₂ and of the a axis of 2H-NbSe₂ have been measured between 4 K and 360 K. Discontinuities in the lattice parameters of TaS₂ were observed at the known charge density wave phase transitions near 200 K and 352 K, and a new transition was found near 283 K. These results are used to estimate the entropy changes occurring at the phase transitions. At the charge density wave onset temperature in NbSe₂ we find an upper limit to any discontinuity in the a axis of 2 × 10^-7 and to any discontinuity in the expansion coefficient of 3 × 10^-7 K^-1.     

Self-, N2- and O2-broadening coefficients for the CO2 transitions near-IR measured by a diode laser photoacoustic spectrometer

Using a high-resolution tunable diode laser photoacoustic spectrometer, self-, N₂ and O₂ pressure broadening coefficients for the first 11 transitions of ¹²C¹⁶O₂ in the R branch of the (30012) ← (00001) overtone band at the 6348 cm⁻¹ have been revisited at room temperature (∼298 K). Air-broadening parameters have also been calculated from the N₂ and O₂ measurements. The dependence of the broadening on rotational quantum number m is discussed. The recorded lineshapes are fitted with standard Voigt line profiles in order to determine the collisional broadening coefficients of carbon dioxide transitions. The results are compared to our previous measurements and to the values reported in the HITRAN04 database and by other research group with a different spectroscopic technique.