The 2CH excitation band in C2H2–N2O and 2CH+torsion combination bands in C2H2–N2O and C2H2–CO2

A preliminary analysis of the 2CH excitation band in C₂H₂–N₂O in the 1.5 µm range (K. Didriche, C. Lauzin, P. Macko, M. Herman and W.J. Lafferty, Chem. Phys. Letters 469, 35 (2009).), only considering 117 low J-, and K_a - vibration-rotation lines, is significantly extended thanks to the analysis of new spectra including very regular series of lines with J/K_a up to 31/15. 1271 b-type lines were assigned. Perturbations are briefly discussed. The rotational temperature in the experiments is estimated to be 20?K and the upper state mean half-time is 1.6?ns for non perturbed levels. The previous analyses of the 2CH + torsion band in C₂H₂–N₂O and in C₂H₂–CO₂ (C. Lauzin, K. Didriche, T. Földes and M. Herman, Mol. Phys. 109, 2105 (2011).), are also extended to include 286 and 234 lines, respectively, also correcting for calibration errors. New rotational constants are obtained using a rigid rotor Hamiltonian by simultaneously fitting the ground, 2CH and 2CH + torsion states in C₂H₂–N₂O, and the latter state, only, in C₂H₂–CO₂.     

The infrared spectrum of 12C2HD: the stretching–bending combination bands in the 1800–4700 cm−1 region

The infrared spectrum of ¹²C₂HD has been observed between 1800 and 4700?cm^?1 by Fourier transform spectroscopy. The ν₁, ν₂ and ν₃ absorption bands and the associated hot and combination bands involving the bending modes up to υ_t?=?υ₄?+?υ₅?=?2 have been investigated. Altogether, 60 vibrational bands were analysed, leading to the spectroscopic characterization of 31 vibrationally excited states. Several perturbations have been observed, but the transitions involving the perturbing states have not been detected. As a consequence, an appropriate treatment of the vibrational or ro-vibrational interactions has not been possible. A tentative assignment of the perturbing states has been proposed. Eventually, global fits for each fundamental vibration and its associated cold and hot bands have been performed.     

SF6 and H2 Broadening and Shifting in the Fundamental Vibrational–Rotational Band of Hydrogen Fluoride

Optics and Spectroscopy - SF6 and H2 broadening and shift of the vibration–rotation lines in the fundamental band of hydrogen fluoride have been investigated. Using mathematical modeling of...     

Rovibrational spectra of the Ar–D2O and Kr–D2O van der Waals complexes in the v2 bend region of D2O

Rovibrational spectra of Ar–D₂O and Kr–D₂O complexes are measured in the v₂ bend region of D₂O monomer using a tunable mid-infrared diode laser spectrometer. One para and two ortho bands for both complexes are identified and then analyzed in terms of a nearly free internal rotor model. Molecular constants for the excited vibrational states, including band-origin, rotational and centrifugal distortion constants, and Coriolis coupling constant, are determined accurately. A comparison of the observed band-origins of Ar–D₂O and Kr–D₂O with the previous results of Ne–D₂O shows regular trends of shift from Kr–D₂O to Ne–D₂O.     

Infrared spectra of acetylene–water complexes: C2D2–H2O,C2D2–HDO,and C2D2–D2O

Infrared spectra of C₂D₂–water complexes are studied in the 4.1 μm region of the C₂D₂ ν₃ fundamental band using a tunable diode laser source to probe a pulsed supersonic slit jet. Relatively large vibrational red shifts (?27.7 to ?28.0 cm^?1) are observed which are more easily interpretable than for the analogous C₂H₂ vibration thanks to the absence of Fermi resonance effects for C₂D₂. Noticeable homogeneous line broadening leads to estimates of upper state predissociation lifetimes of about 0.5, 0.9 and 1.1 ns for C₂D₂–H₂O, –HDO, and –D₂O, respectively. Transitions involving K_a = 0 and 1 levels are observed for C₂D₂–HDO, but there is a puzzling absence of K_a = 1 for C₂D₂–H₂O and C₂D₂–D₂O.     

Analysis of the High-Resolution Rovibrational Spectrum of the C2H2D2-cis Molecule in the Region 1620–1780 cm–1

Russian Physics Journal - The spectrum of the cis-ethylene-d2 molecule (C2H2D2-cis) has been recorded with a Bruker IFS 120 HR Fourier spectrometer in the wavelength region 1100–2000...     

The absorption spectrum of 12C2D2 in the 10000–12500 cm−1 spectral region

The absorption spectrum of dideuteroacetylene has been recorded by intracavity laser absorption spectroscopy (ICLAS) in the 10 200–12 500cm^?1 spectral region. Among 25 absorption bands of ¹²C₂D₂ rotationally analysed in this spectral region, 17 are newly observed. They include one II_u-Σ⁺ _g and thirteen Σ⁺ _u-Σ⁺ _g bands starting from the vibrational ground state and eleven hot bands from the V ₄ = 1 and V ₅ = 1 lower states. The rotational structure of two excited levels is affected by a strongly J-dependent interaction with a perturber which induces intensity transfer to extra lines. The coupling is identified as a I-resonance interaction with δ_u dark states and the vibrational assignment of the perturbers is discussed. Two Σ-Σ bands of the ¹²C¹³ CD₂ species, present in natural abundance in the sample, could also be identified and rotationally analysed. Most of the corresponding excited vibrational levels of ¹²C₂D₂ were unambiguously assigned using the polyad model [Herman, M., el idrissi, M. I., Pisarchik, A., Campargue, A., Gaillot, A.-C., Biennier, L., di lonardo, G. and Fusina, L., 1998, J. chem. Phys., 108, 1377] which allows vibrational energies and B _V rotational constants to be predicted. In particular the previously highlighted 1/244 anharmonic resonance is confirmed by energy and intensity features in several {(V ₁, V ₂, V ₃, V ₄ = 0, V ₅ = 0),(V ₁ ?1, V ₂ + 1, V ₃ V ₄ = 2, V ₅ = 0)} dyads. Significant deviations between predicted and experimental energy levels are observed for a few levels and discussed.     

High resolution infrared and Raman spectroscopy of ν 2 and associated combination and hot bands of 13C12CD2

Infrared and Raman spectra of dideuterated acetylene containing one ¹³C atom, ¹³C¹²CD₂, have been recorded and analysed to obtain detailed information on the fundamental ν ₂ band and associated combination and hot bands. Infrared spectra were recorded at 4?×?10^?3?cm^?1 resolution in the region 1150?2900^?cm^?1, which contains combination and hot bands from the ground and the bending v ₄?=?1 and v ₅?=?1 states. The Q-branches of the ν ₂ fundamental and associated hot bands (ν ₂?+?ν ₄???ν ₄, ν ₂?+?ν ₅???ν ₅, ν ₂?+?2ν ₄???2ν ₄, ν ₂?+?2ν ₅???2ν ₅ and ν ₂?+?ν ₄?+?ν ₅???(ν ₄?+?ν ₅)) were recorded using inverse Raman spectroscopy, with an instrumental resolution of about 3?×?10^?3?cm^?1. In addition, the observation of the 2ν ₂???ν ₂ Raman band was carried out populating the v ₂?=?1 state by stimulated Raman pumping. In total, 11 Raman and 9 infrared bands were analysed, involving all the l-vibrational components of the excited stretching?bending manifolds up to v _t ?=?v ₄?+?v ₅?=?2.

A simultaneous analysis of all infrared and Raman assigned transitions has been performed on the basis of a theoretical model which takes into account the rotation and vibration l-type resonances within each vibrational manifold and the Darling?Dennison anharmonic resonance between the ν ₂?+?2ν ₄ and ν ₂?+?2ν ₅ states. The parameters obtained reproduce the assigned transition wavenumbers with a standard deviation of the same order of magnitude as the experimental uncertainty.     

The refractivity of CO2 gas in the region of 10 μm

The refractivity of the CO₂ gas is measured with an experimental error of 2% in the 10-m region, using 10.4-m band CO₂ laser line. The frequency of the CO₂ laser is swept through the Doppler profile of the laser line. The experiment is achieved using a 0.63-m He–Ne/10.6-m CO₂-laser interferometer with a 2-m long vacuum cell. From the result, it is found that the Koch's formula also holds for the wavelengths in the 10-m region within an accuracy of 2%.     

Intense spontaneous amplified emission of Li2 diffuse violet bands in the 4400 Å region

We report observation of intense spontaneous amplified radiation of Li₂ diffuse violet band in the 4100–4900 Å region. The radiation is strongly enhanced when the lithium vapor in a heat pipe is optically pumped with a pulsed dye laser with the output wavelength tuned to near the Li 2s–4s two-photon resonance transition. The diffuse violet band can probably be assigned to a recently reported triplet bound-free (2³ _g a ³ _u ⁺ ) transition. It is found that the productions of the molecular diffuse band are contributed from Li atoms as well as Li₂ molecules. The excitation functions and their dependence on laser power density are presented and the mechanisms for producing the diffuse bands are discussed.Department of Physics, National Central University, Chung-Li, Taiwan, Republic of Chinabl]References     

Calculation of H+-ranges and H+-range stragglings in the energy region 1–1000 keV

The use of various approximations in calculating proton projected ranges has been studied by the analytical and the Monte Carlo methods. A correction is presented for the projected ranges given in the compilation (Andersen and Ziegler: Hydrogen Stopping Powers and Ranges in All Elements). The greatest correction factors at 1, 10, 100 and 1000 keV are 3.5, 2.1, 1.4 and 1.2, respectively. The corrections result from the inclusion of the tabulated electronic stopping power values in the calculation of the projected ránge to the total range ratio and from the estimation of the effect of the reflection. The Monte Carlo calculations show the electronic straggling to be a remarkable factor in the width of the proton range distributions at reduced energies larger than of the order of 100.     

High-resolution infrared spectroscopy of H12C13CD and H13C12CD in the 470–5200 cm−1 spectral region

The fundamental ro-vibrational bands and the 2ν₄?←?GS, 2ν₅?←?GS, 2ν₃?←?GS, ν₄?+?ν₅?←?GS, ν₃?+?ν₄?←?GS, ν₃?+?ν₄?←?ν?₄, ν₃?+?ν₅?←?ν₅, overtone, combination and hot bands of the two rare isotopologues of acetylene H¹²C¹³CD and H¹³C¹²CD have been detected by Fourier transform infrared spectroscopy (FTIR). The analysis of the data has provided very accurate rotational and vibrational parameters for the ground and for the vibrationally excited states.     

Electromotive force of a COCO2 sensor in COCO2H2H2O atmospheres and simultaneous determination of partial pressures of CO and CO2

The electromotive force (EMF) of the COCO₂ sensor using Na₂CO₃ and NASICON (Na₃Zr₂Si₂PO₁₂) as solid electrolytes has been examined in COCO₂Ar atmospheres. The EMF is related to the partial pressures of CO and CO₂ and proportional to log(P²_CO2P⁻¹_CO). The simultaneous use of the oxygen sensor of stabilized zirconia gives the EMF proportional to log(P_CO2P⁻¹_CO). The EMF's of two sensors permit to determine individually partial pressures of CO and CO₂. The existence of H₂ with high concentration does not affect the EMF's. This fact proves the applicability of the two-sensor system to the monitoring and the controlling of reducing atmospheres in industrial processes.     

Accurate ground-state potential energy surfaces of the C2H2–Kr and C2H2–Xe van der Waals complexes

Accurate ab initio intermolecular potential energy surfaces (IPES) have been obtained for the first time for the ground electronic state of the C₂H₂–Kr and C₂H₂–Xe van der Waals complexes. Extensive tests, including complete basis set and all-electron scalar relativistic results, support their calculation at the CCSD(T) level of theory, using small-core relativistic pseudopotentials for the rare-gas atoms and aug-cc-pVQZ basis sets extended with a set of 3s3p2d1f1g mid-bond functions. All results are corrected for the basis set superposition error. The importance of the scalar relativistic and rare-gas outer-core (n–1)d correlation effects is investigated. The calculated IPES, adjusted to analytical functions, are characterized by global minima corresponding to skew T-shaped geometries, in which the Jacobi vector positioning the rare-gas atom with respect to the center of mass of the C₂H₂ moiety corresponds to distances of 4.064 and 4.229?Å, and angles of 65.22° and 68.67° for C₂H₂–Kr and C₂H₂–Xe, respectively. The interaction energy of both complexes is estimated to be ?151.88 (1.817?kJ?mol^?1) and ?182.76?cm^?1 (2.186?kJ?mol^?1), respectively. The evolution of the topology of the IPES as a function of the rare-gas atom, from He to Xe, is also discussed.     

H2-broadening,shifting and mixing coefficients of the doublets in the ν2 and ν4 bands of PH3 at room temperature

The broadening, shifting and mixing coefficients of the doublet spectral lines in the ν₂ and ν₄ bands of PH₃ perturbed by H₂ have been determined at room temperature. Indeed, the collisional spectroscopic parameters: intensities, line widths, line shifts and line mixing parameters, are all grouped together in the collisional relaxation matrix. To analyse the collisional process and physical effects on spectra of phosphine (PH₃), we have used the measurements carried out using a tunable diode-laser spectrometer in the ν₂ and ν₄ bands of PH₃ perturbed by hydrogen (H₂) at room temperature. The recorded spectra are fitted by the Voigt profile and the speed-dependent uncorrelated hard collision model of Rautian and Sobelman. These profiles are developed in the studies of isolated lines and are modified to account for the line mixing effects in the overlapping lines. The line widths, line shifts and line mixing parameters are given for six A₁ and A₂ doublet lines with quantum numbers K = 3n,?(n = 1,?2, …) and overlapped by collisional broadening at pressures of less than 50 mbar.     

Diode laser measurements of air and nitrogen broadening in the ν2 bands of HDO,H216O,and H218O

Pressure-broadening coefficients for several rotation-vibration lines in the ν₂ bands of HDO, H₂¹⁶O, and H₂¹⁸O have been determined from laboratory spectra recorded in the 1260- to 1360-cm⁻¹ region with a tunable diode laser spectrometer system. Air and nitrogen were used as the broadening gases and, for all the measured transitions, the nitrogen-broadened half-widths were found to be consistently larger than the corresponding air-broadened half-widths by about 12%. The results have been compared to previously published values when appropriate.     

Diode laser measurement of line strengths and air-broadening coefficients of CO2 and CO in the 1.57 μm region for combustion diagnostics

Spectral measurements of two line pairs of CO₂ and CO in the temperature range 300–1000 K at 1.573 µm were performed using a fiber-coupled distributed feedback (DFB) diode laser. The two line pairs can be used in a tunable diode laser (TDL) absorption sensor for simultaneously detecting CO₂ and CO gas in a single scan of the diode laser. The spectral parameters (line strengths, air-broadening coefficients and the temperature exponent n) of the two pairs are presented. The measured data agree well with existing databases (HITRAN 2004 and HITRAN 2008), the discrepancies being less than 5% for most of the probed transitions. Although the HITRAN database is a useful tool for sensor design, we found that laboratory measurements of the spectroscopic data for the line pair selected for high-temperature sensors are necessary for establishing the uncertainty for accurate measurements.