Microwave spectrum of PHD: hyperfine structure

The rotational spectrum of the monodeuterated PH₂ radical was studied using a source-modulated submillimeter-wave spectrometer. The PHD radical was generated in a free space absorption cell by a dc-glow discharge in a gas mixture of PH₃ and D₂. Six a-type and 20 b-type rotational transitions were observed in the frequency region of 170-670 GHz. Hyperfine structure due to the deuterium nucleus was resolved only in the rotational transitions of 1₁₁-0₀₀ and 1₁₀-1₀₁ and in the low F₂ components of N=2-1 transitions. A total of 219 spectral lines were measured of which 145 were analyzed by least-squares methods. These yielded 34 precise molecular constants including the hyperfine coupling constants of phosphorus, hydrogen, and deuterium. The principal axes and principal values of the magnetic dipole coupling tensors of hydrogen in PH₂ and deuterium in PD₂ were derived from the observed values of PHD, PH₂ and PD₂. The principal axis of the hydrogen magnetic dipole coupling tensor in PH₂ makes an angle of 2.29° with the PH bond and its T_σ and T_⊥ principal values are determined to be 12.93 and −18.39 MHz, respectively.     

Spectral intensities in the ν1 band of carbonyl sulfide and its isotopic species

A tunable diode laser was used to perform measurements of absolute lines intensities in the ν₁ fundamental of carbonyl sulfide. Spectra have also been recorded for the following isotopic species: ¹⁶O¹²C³⁴S, ¹⁶O¹³C³²S and ¹⁶O¹²C³³S. The vibrational band strength S_v⁰ was calculated at 298 K. The absolute intensity for 100% of ¹⁶O¹²C³²S species is found to be S_v⁰ = 29.69 ± 0.15 cm⁻² atm⁻¹ with the uncertainty covering three times the standard deviation. We have tried to determine the α-coefficient involved in the Hermann-Wallis factor F = (1 + αm + )² and the value is found to be negligible (−5 ± 8) × 10⁻⁵. The S_v⁰ value obtained for the other isotopic species is very close to the normal one.     

Emission spectrum of MgCl molecule in 5030-4380Å

The emission spectrum of diatomic magnesium chloride molecule has been reinvestigated in the region 5030-4380 Å (B ²Σ⁺ —A ²Π transition) at a higher dispersion. The vibrational assignments of the bands are confirmed by observing the vibrational isotope shifts due to isotopes of magnesium and chlorine. Precise values of the vibrational constants are determined for theB ²Σ⁺ state.     

Estimation of glucose absorption spectrum at its optimum pathlength for every wavelength over a wide range

ABSTRACT

A method to estimate the absorbance spectrum caused by the variation in the concentration of a substance in a medium at the optimum pathlength for every wavelength on a wide waveband without adjusting the cell’s size precisely was presented in the paper. This spectrum could be used to evaluate the absorption of certain substance at the optimum pathlength at each wavelength, instead of using a uniform pathlength like absorption coefficient. And the absorbance spectra of glucose in aqueous solution at optimum pathlength for every wavelength at 900–2500?nm were estimated by using this method. Moreover, the glucose absorbance spectra show an unexpected result that the absorption peaks at different overtones of the oxygen–hydrogen and carbon–hydrogen bonds are of similar amplitudes.     

Microwave spectrum of isotopic species of urea (NH2)2CO

We report new microwave measurements for the (¹⁵NH₂)₂CO and (¹⁴NH₂) (¹⁵NH₂)CO isotopologues of urea. The spectra were recorded between 5 and 20 GHz with our MWFT spectrometer coupled to a newly built heated nozzle. A new centrifugal distortion analysis was performed for the (¹⁵NH₂)₂CO species including all available data. For the (¹⁴NH₂) (¹⁵NH₂)CO species the hyperfine structure was recorded for the first time.     

Spectroscopic studies of CO2 trapped in rare gas matrices

Low temperature (5 K) high resolution (0.15 and 0.03 cm⁻¹) absorption spectra of ¹³CO₂ have been recorded in neon, argon, krypton, and xenon matrices, in the ν₃ and ν₂ regions. Diffusion experiments have been performed in krypton and xenon in order to identify vibrational traps which could be responsible for the decrease and shortening of the emission observed after laser excitation: high-frequency structures in the ν₃ region are assigned to dimers and a doubling of the monomer line is due to a site effect. In neon, only a double substitutional site, with a splitting of the degenerate ν₂ vibration, is observed. In argon, as previously reported, a single and a double site are characterized. In krypton and xenon, where ν₂ is not split, only single sites would be predicted. As one of them exhibits a ν₃ line highly sensitive to temperature, we expect a large coupling with the lattice and a fast vibrational relaxation. This site is very likely the vibrational trap we are looking for.     

Microwave spectra of carbonyl sulfide: Measurements of ground state and vibrationally excited 16O13C32S, 18O12C32S,and other isotopic species

Microwave measurements have been made on isotopically enriched samples of ¹³C-carbonyl sulfide and ¹⁸O-carbonyl sulfide. Centrifugal distortion constants and l-type doubling constants have been determined for these isotopically substituted molecules. Rotational constants have been measured for all vibrational states below 2150 cm^?1 and B_e values have been determined. The equilibrium bond distances calculated from different pairs of isotopes are compared and a substitution equilibrium structure is given. Some new measurements are also reported for the isotopic species ¹⁸O¹³C³²S, ¹⁸O¹³C³⁴S, ¹⁸O¹²C³⁴S, and ¹⁶O¹³C³⁴S.     

基于样片厚度精确估计的THz吸收系数谱算法

利用太赫兹时域光谱技术(THz-TDS)提取物质在太赫兹波段的吸收系数谱是太赫兹应用的一个重要方面。由于样品的吸收系数与其厚度存在着复杂的非线性关系,而厚度又不便于直接准确测量,往往造成吸收系数谱的失真。根据Duvillaret等用于LiNbO3的厚度估计方法,改进了谷氨酰胺(Gln)与组氨酸(His)在0.3～2.6THz(1THz=1012 Hz)波段的吸收系数谱的测定和计算。为了说明改进后的吸收系数谱的合理性,设计了一系列实验对比了同种氨基酸在不同浓度下吸收系数的线性符合程度。结果表明,改进后计算出的氨基酸吸收系数与浓度之间存在更好的线性关系,符合Lambert-Beer定律的描述,这为进一步的定量分析奠定了基础。     

The isotopic dependence of the spin-rotation interaction: the rotational spectrum of cadmium hydride in its XΣ state

Far-infrared rotational transitions within the X²Σ⁺ (v=0) state of cadmium hydride (CdH) were recorded over the range N″=2-17 for 12 different isotopomers, using the technique of tunable far-infrared (TuFIR) spectroscopy. The molecule was made by heating cadmium metal in the presence of a DC electric discharge in hydrogen. Fine structure arising from the electron spin-rotation interaction and hyperfine structure from the ¹¹¹Cd, ¹¹³Cd, and ¹H nuclei were resolved and analyzed. All of the isotopic data were fitted together using a Hamiltonian containing mass-independent, Dunham-type rotational parameters U_kl and small correction terms Δ_kl described by Watson [J. Mol. Spectrosc. 80 (1980) 411]. The spin-rotation interaction was modeled in an analogous way using Dunham-like U_γ,kl parameters, and fitting its isotopic dependence properly required the use of four Δ_γ,kl correction terms.     

Rotational spectrum of the Ar–dimethyl sulfide complex

The rotational spectra of three isotopomers of the Ar–dimethyl sulfide (DMS) complex – normal, ³⁴S, and ¹³C species – were measured in the frequency region from 3.7 up to 24.1 GHz by Fourier transform microwave spectroscopy. The normal species yielded 43 a-type and 79 c-type transitions. No Ar tunneling splitting was observed, while many transitions were split by the internal rotation of the two methyl tops of the DMS unit. In cases where the K-type splitting was close to that due to methyl internal-rotation, several forbidden transitions were observed that followed b-type selection rules. All of the observed transition frequencies were analyzed simultaneously using a phenomenological Hamiltonian also used in previously published work describing the Ar–dimethyl ether (DME) and Ne–DME complexes. The rotational and centrifugal distortion constants and the potential barrier height to methyl-top internal rotation, V₃, were determined. The rotational constants were consistent with an Ar–DMS center of mass (cm) distance of 3.796 (3) Å and a S–cm–Ar angle of 104.8 (2)°. The V₃ potential barrier obtained, 736.17 (32) cm⁻¹, was 97.8% of the DMS monomer barrier. By assuming a Lennard–Jones-type potential, the dissociation energy was estimated to be 2.4 kJ mol⁻¹, which was close to the value for Ar–DME, 2.5 kJ mol⁻¹.     

First-principles study of the effect of heavy Ni doping on the electronic structure and absorption spectrum of wurtzite ZnO

The band structures, densities of states and absorption spectra of pure ZnO and two heavily Ni doped supercells of Zn_0.9722Ni_0.0278O and Zn_0.9583Ni_0.0417O have been investigated using the first-principles plane-wave ultrasoft pseudopotential method based on the density functional theory. The calculated results showed that the band gap is narrowed by Ni doping in ZnO; this, is because the conduction band undergoes a greater shift toward the low-energy region than the valence band and because heavier doping concentrations lead to, narrower band gaps. Moreover, the optical absorption edge exhibits a redshift due to the narrowing of the band gap. Heavier doping concentrations leads to more significant redshifts, which is in agreement with the experimental results.     

Measurements of coating density using ultrasonic reflection coefficient phase spectrum

A nondestructive method to determine the density of coating has been proposed in this paper based on the ultrasonic reflection coefficient phase spectrum (URCPS). A model was set up first to represent the ultrasonic waves reflected from a coating system at normal incident, and the relation between the extremum of URCPS and the coating density was established to provide the principle of determining the density. The ultrasonic method was validated on a series of ZrO2-7 wt.%Y2O3 (YSZ) coatings with various density. The specimens were prepared by electric beam physical vapor deposit (EB-PVD). After deposition, the specimens were irradiated using high-intensity pulsed ion beam (HIPIB) at different ion current density of 100 and 200 A/cm2 to change coating density. The coating densities of as-deposited and post irradiation by HIPIB were derived to be 4940-5030, 5200-5320 and 5390-5470 kg/m3, respectively. The relative error between the coating density measured by the ultrasonic method and Archimedean principle ranging from 2.53% to 6.11%, indicates that the proposed ultrasonic quantification method provides a reliable nondestructive way to determine coating density.     

On the water-induced critical double point in a polymer solution: the role of isotopic substitution

This paper examines the effect of substitution of water by heavy water in a polymer solution of polystyrene (molecular weight=13000) and acetone. A critical double point (CDP), at which the upper and the lower partially-miscible regions merge, occurs at nearly the same coordinates as for the system [polystyrene+acetone+water]. The shape of the critical line for [polystyrene+acetone+heavy water] is highly asymmetric. An explanation for the occurrence of the water-induced CDP in [polystyrene+acetone] is advanced in terms of the interplay between contact energy dissimilarity and free-volume disparity of the polymer and the solvent. The question of the possible existence of a one-phasehole in an hourglass phase diagram is addressed in [polystyrene+acetone+water]. Our data exclude such a possibility.     

Global fit of the high-resolution infrared spectrum of D2S

High-resolution Fourier-transform spectra of the D₂S molecule in the regions of polyads of interacting vibrational states v = 3/2, 2, 5/2, 3 and 7/2 (v = v₁ + v₂/2 + v₃) were recorded for the first time with a Bruker IFS 120 Fourier-transform interferometer and analysed. A global fit of all currently available rotation-vibration energies has been made for 22 vibrational states of the D₂S molecule. The resulting set of 231 parameters reproduces all the initial experimental data (about 3670 vibration-rotation energies which correspond to more than 9700 ro-vibrational transitions with J^max = 25) with accuracies close to the experimental uncertainties.     

Multi-resolution error analysis of predicted absorption coefficients. Method and application to the infrared spectrum of methane at high temperature

A general method for the estimation of the confidence interval of molecular absorption coefficients is presented. Statistical numerical experiments are implemented to quantify the propagation of errors from line parameters to absorption coefficients as a function of the resolution. The method uses line parameter predictions (position and intensity) with estimated uncertainties derived from global polyad models. This work is especially intended to provide expert information for applications requiring theoretical predictions for which the present state of the art of line by line high-resolution modeling is not accurate enough to meet the desired precision. As an illustration, it is applied to predict the absorption coefficient of methane at high temperature involving simultaneously well known lower energy levels (cold bands) and higher energy levels with much lower precisions (hot bands). Potential extensions are discussed in the context of atmospheric remote sensing of astrophysical objects.     

Accurate second Kerr virial coefficient of rare gases from the state-of-the-art ab initio potentials and (hyper)polarizabilities

The second Kerr virial coefficient of rare gases is studied in this work using the best ab initio potentials and (hyper)polarizabilities in the literature. The second Kerr virial coefficient of helium-4, helium-3, neon, argon, and krypton and its polarizability component of xenon are computed by the semi-classical method together with the Padé approximant over a wide temperature range. In addition, the uncertainty of second Kerr virial coefficient is estimated from the uncertainties of the ab initio interaction-induced properties. The experimental and theoretical data in the literature is compared with our calculated values to examine the quality of this work. It is shown that our computed values in the supplementary materials are as accurate as the literature data at medium and high temperatures and are more reliable at low temperatures.     

Microwave spectrum of deutero propargyl mercaptan HCCCH2SD: Investigation of the internal rotation in the -SH and -SD isotopic species

The microwave spectrum of the deuterated propargyl mercaptan was recorded and measurements in the torsional levels 0^± and 1^± are reported. The internal rotation analysis is carried further using the new data obtained and a more specific Hamiltonian. With the mean values of the rotational constants for the two isotopic species in the states 0^±, a r₀-structure is proposed.     

Two photon optogalvanic spectrum of theD-X system of HgBr

Two photon laser optogalvanic spectrum of theD-X system of HgBr molecule has been recorded using Nd-YAG laser pumped dye laser for the first time. A large number of new bands involving higher vibrational levels have been observed. Isotopic heads due to the two bromine isotopes have been observed and used in fixing the vibrational assignment. Vibrational constants for theX andD states of the two isotopic molecules have been determined.     

The lowest 4f-to-5d and charge-transfer transitions of rare earth ions in YPO4 hosts

In order to study the high-energy optical transitions i.e. 4f-to-5d (f–d) and charge-transfer (CT) spectra of trivalent rare earth (4fⁿ-series, lanthanide) ions in crystal lattices, the luminescence excitation spectra of the series ions in YPO₄ host lattices are measured in a VUV–UV spectral region of 120–350 nm. The f–d bands are observed with all of the series ions except for the ions with the transition energy higher than the host lattice absorption edge i.e. except for Gd³⁺ and Yb³⁺, and the CT bands are observed except for Ce³⁺, Gd³⁺ and Tb³⁺ (Pm is unavailable).

Jørgensen's formulation which has elucidated the systematic variation of the energies of the f–d and CT transitions through the 4fⁿ-series is modified in a form of a single-electron scheme. The many-electron effects in the scheme are calculated and presented as a numerical table. The energies of the observed f–d and CT bands fit well with those calculated by the use of this table.     

Ultrasonic characterization of thermally grown oxide in thermal barrier coating by reflection coefficient amplitude spectrum

The thermally grown oxide (TGO) growth at the interface of ceramic coating/bond coating in thermal barrier coatings (TBCs) was evaluated by ultrasonic reflection coefficient amplitude spectrum (URCAS). A theoretical analysis was performed about the influence of acoustic impedance match relationship between the ceramic coating and its adjacent media on URCAS. The immersion ultrasonic narrow pulse echo method was carried out on the TBC specimen before and after oxidation under 1050 °C × 1 h for 15 cycles. The resonant peaks of URCAS obtained before and after oxidation showed that TGO which generated between the ceramic coating and bond coating due to the oxidation, changed the acoustic impedance match between the ceramic coating and its adjacent media. This method is able to nondestructively characterize the generation of TGO in TBCs, and is important to practical engineering application.