High-Resolution Infrared Studies of ν1, 2ν1, and 2ν4 Bands of CHCl3

The C-H stretching fundamental band ν₁ (3033 cm⁻¹) of chloroform CH³⁵Cl₃ has been investigated together with the first overtone 2ν₁ (5941 cm⁻¹) in order to determine the rotation vibration parameters. From the ν₁ band α₁^C=−0.025 46(41)×10⁻³ cm⁻¹ and α₁^B=−0.010 688(44)×10⁻³ cm⁻¹ were obtained. The hot bands connected to the low lying fundamentals ν₃ and ν₆ have been analyzed and anharmonicity constants have been derived. Both the parallel and the perpendicular component band of the C-H bending overtone 2ν₄ have also been studied. In the parallel band (2410 cm⁻¹) more than 900 lines were included in the fit. In the perpendicular band (2443 cm⁻¹) 2615 lines were fitted using a model with one resonance. Among other things the results C₀−C_v=0.025 262 (20)×10⁻³ cm⁻¹, B₀−B_v=0.134 883 (25)×10⁻³ cm⁻¹, and (Cζ)_v=−0.111 867 56 (30) cm⁻¹ were obtained.     

Absorption spectra of C6H6 and C6D6 near 340 nm

The absorption spectra of C₆H₆ and C₆D₆ in the liquid phase have been studied near 340 nm. The absorption spectrophotometric mounting was a sequential double-beam attachment with linear response to energy on scanning of the spectrum before the exit slit and an electronic device which gives directly either the absorbance or the integrated absorbance of a transition and, consequently, its oscillator strength.The oscillator strength measured for the band of C₆H₆ is 8×10^?8, which corresponds to a dipole moment of 2.4×10^?3 Debye; this value is of the same order as a theoretical value calculated by Tsubomura and Mulliken (3.8×10^?3 Debye) for a transition between states ³F and ³A of an oxygen-benzene pair. This agreement corroborates the hypothetical existence of such a transition.The first vibrational band is at 28553 cm^?1 for C₆H₆; this band is not observed in the vapor or solid phase. It corresponds probably to the transition 0-0, which is considered in the literature to be near 29500 cm^?1. The isotopic shift measured for this first band is 164 cm^?1. The vibrational frequencies are, respectively, 910 cm^?1 for C₆H₆ and 889 cm^?1 for C₆D₆.     

Eu3+掺杂的Sr2CeO4发光材料的光致发光研究

利用高温固相反应法制备了Eu³⁺掺杂的Sr₂CeO₄样品,并对其吸附水前后的光谱特性进行了研究.结果发现,对于刚制备的Sr_2-xEu_xCeO_4+x/2样品, 在Ce⁴⁺—O^2-的电荷迁移激发中,只有强激发带(～35700cm^-1)与Eu³⁺离子间存在能量传递,而弱激发带 (～29400cm^-1)只是引起Ce⁴⁺—O^2-的电荷迁移发射;在Sr_2-xEu_xCeO_4+x/2样品吸附水后,Eu³⁺的线状吸收跃迁强度显著增加, Ce⁴⁺—O^2-两个激发带均向Eu³⁺离子传递能量. Ce⁴⁺—O^2-强激发带通过交换作用向Eu³⁺离子传递能量,而弱激发带与Eu³⁺离子间的能量传递机理是非辐射多极子近场力的相互作用. 关键词： 2-xEu_xCeO_4+x/2')" href="#">Sr_2-xEu_xCeO_4+x/2 发光性质 能量传递 吸附水     

Two-exciton transition in the antiferromagnetic KNiF3 and K2NiF4

For the sharp band located at 31,200 cm^?1 in the three dimensional antiferromagnetic KNiF₃, the dependence of the oscillator strength on the Ni ion concentration and the stress-induced linear dichroic spectrum are studied. The polarization dependence of the corresponding band in the two dimensional antiferromagnetic K₂NiF₄ is also measured. The weak structure located at 30,780 cm^?1 is assigned as two-exciton transition, and the band at 31,200 cm^t?1 as a two-exciton transition accompanied with a T_1u phonon.     

Analysis of the absorption spectrum of 12CD4 between 2180 and 2320 cm−1. Comparative study of ν3 and 2ν3

The high-resolution spectrum of the ν₃ band of ¹²CD₄ has been recorded and analyzed. Corresponding to 367 allowed transitions of this band, 218 lines have been identified between 2180 and 2320 cm^?1. Twelve significant spectral constants have been determined in such a way as to reproduce the spectrum with a standard deviation equal to 7 × 10^?3 cm^?1.A comparative analysis between the present results on ν₃ and those obtained by K. Fox [J. Mol. Spectrosc.9, 381 (1962)] for 2ν₃ showed that the interaction between the two sub-levels E and F₂ of the v₃ = 2 state produces a significant effect of the second order and enabled us to determine the interval between these sublevels, i.e., 20 T₃₃ ～ 30 cm^?1.     

Analysis of the ν2 and ν4 infrared bands of CD4

The infrared spectrum of totally deuterated methane CD₄ has been recorded between 930 cm^?1 and 1180 cm^?1 under high resolution (0.003 cm^?1). The ν₂ and ν₄ bands of ¹²CD₄ have been reanalyzed on the basis of a complete third-order Hamiltonian including all the coupling terms linking the upper states of the two bands. A set of only 16 self-consistent parameters have been adjusted to fit more than 1650 assigned transitions reaching a maximum upper state J value of 20. The obtained standard deviation is 0.0041 cm^?1. In addition, 171 lines of the ν₄ band of ¹³CD₄ have been assigned. They have been analyzed, in the same dyad scheme, by adjusting 7 parameters of the ν₄ band together with the main ζ₂₄ Coriolis parameter. The obtained standard deviation is only 0.0012 cm^?1.     

Absolute intensities and pressure broadening coefficients measured at different temperatures for the 201II ← 000 band of 12C16O2 at 4978cm-1

Absolute line intensities and self-broadening coefficients have been measured at 197° and 294°K for the 201_II ← 000 band of ¹²C¹⁶O₂ at about 4978cm^-1. The vibration-rotation factor (F_VR), the purely vibrational transition moment (∣R(O)∣), and the integrated band intensity (S_band) are deduced from the measurements. The results are: F_VR(m)=1+(0.24±0.08)x10^-4m+(0.55+0.21)x10^-4m², ∣R(O)∣= (4.340±0.008x10^-3 debye, S_band=96372±190cm^-1km^-1atm^-1_STP. The results for self-broadening coefficients, as well as for individual vibration-rotation lines, are presented in the text.     

The ν3 band of CD3I around 500 cm−1

The region of the lowest fundamental band ν₃ of CD₃I around 500 cm^?1 is studied at a resolution of 0.015 cm^?1. The K structure in the parallel band ν₃ is resolved for K = 6 – 14. Molecular constants for the ν₃ level are derived, including α₃^A = 3.055(13) × 10^?3 cm^?1. The “hot” band 2ν₃-ν₃ is also investigated.     

High-resolution infrared spectrum of the ν2 + ν3 band of 14N16O2

The ν₂ + ν₃ band of ¹⁴N¹⁶O₂ has been recorded with resolution of 0.028 cm^?1. Ground state and upper state rotational constants have been obtained. The band center obtained, ν₀ = 2355.1517 ± 0.0011 cm^?1 (error cited is 3σ), has been combined with the band centers recently determined for ν₃ and ν₂ to calculate X₂₃ = ?11.348 ± 0.020 cm^?1 where the uncertainty cited is based on reasonable estimates of the absolute frequency error.     

Shubnikov-de haas effect in n-CdSnAs2

Shubnikov-de Haas oscillations in the transverse magnetoresistance of single-crystalline n-type CdSnAs₂ have been recorded at temperatures between 2 and 25 K in magnetic fields up to 5T. The electron concentration of the samples ranged from 2 × 10¹⁷ to 2 × 10¹⁸ cm^?3. The angular dependences of the oscillation periods and cyclotron effective masses showed that the conduction band exhibits an energy dependent anisotropy, obeying the Kildal band structure model. For the low-temperature values of the band parameters we found: a band gap E_g = 0.30 eV, a spin-orbit splitting Δ = 0.50 eV, a crystal field splitting parameter δ = ?0.09 eV, and an interband matrix element P = 8.5 × 10^?8eV cm. This simple four-level model was found to be not adequate to describe quantitatively the observed electronic effective g-factor for a sample with low electron concentration.     

The AE-XA1 System of CaOCH3

We have recorded laser excitation spectra of the CaOCH₃ free radical in a laser ablation molecular beam apparatus, at a spectral resolution of about 0.010 cm⁻¹ and a rotational temperature estimated at 15 K. The two spin-orbit components of the A²E-X²A₁ 0₀⁰ origin band between 625 and 630 nm have been analyzed. Five main subbands were revealed, with ΔK=+1 and K″=0,±1,±2. There was clear evidence of lambda-doubling in the A²E_1/2-X²A₁ 0₀⁰ (F′₁) K′=+1←K″=0 component. A nonlinear least-squares fitting program based on the model developed by Endo et al. [Y. Endo, S. Saito, and E. Hirota, J. Chem. Phys.81, 122-135 (1984)] fit the experimental data (514 A-X lines, N″≤37) with a root mean square deviation of 0.003 cm⁻¹, using known molecular constants of the ground state. The main vibronic (T₀=15 925.1232(5) cm⁻¹), spin-orbit (aζ_ed=66.974 48(51) cm⁻¹), Coriolis (Aζ_t=5.437 30(24)) cm⁻¹, rotational (A=5.439 97(24) cm⁻¹, B=0.117 884(2) cm⁻¹), and fine structure constants (ε₁=−8.208(14)×10⁻³ cm⁻¹, h₁=1.50(12)×10⁻⁴ cm⁻¹, ε_aa=3.58(89)×10⁻³ cm⁻¹, ε_bc=3.20(76)×10⁻³ cm⁻¹) for the excited state have been obtained.     

The high-resolution infrared spectrum of ethane-1,1,1-D3 rovibration analyses of the pseudoperpendicular A1A2ν9 + ν10 band and the parallel ν3 + ν4 and ν5 bands

A complete vibration-rotation analysis was made of the A₁A₂ combination band ν₉ + ν₁₀ of CH₃CD₃ at 2582 cm^?1. This band exhibits pseudoperpendicular structure due to the large effective Coriolis interaction constant (ζ ≈ 0.7), which couples the almost degenerate A₁ and A₂ vibrational components for all nonzero values of the rotational quantum number K, and gives a subband Q-branch spacing of 2.5 cm^?1. The location of the band center is assisted through an interruption of the perpendicular-like structure, since both K = 0 Q branches are forbidden by the vibrational and rotational selection rules. The conventional A₁ parallel bands ν₃ + ν₄ at 2507 cm^?1 and ν₅ (CC stretch) at 905 cm^?1 were also analyzed. For ν₅, a combination of numerical analysis and band contour simulation was used to determine a set of upper-state rotation parameters. Combination of the present results with previous data for ν₉ and 2ν₃ permits rotational parameters to be derived for the ν₄ and ν₁₀ fundamentals of CH₃CD₃. Neither of these fundamentals are amenable to straightforward analysis, both being very weak in the infrared and overlaid by the intense ν₁₁ fundamental.     

Study of the ν2 + ν3 and 2ν6 infrared bands of CH379Br and CH381Br

The rotational analysis of the ν₂ + ν₃ band, centered around 1912 cm^?1, and of both components 2ν₆^±2 and 2ν₆⁰, centered about 1912 and 1904 cm^?1, respectively, has been carried out from a Fourier transform spectrum having a resolution limit of 0.005 cm^?1. A standard deviation of about 0.001 cm^?1 was obtained for about 750 lines of the unperturbed 2ν₆^±2 component for both isotopic species. The ν₂ + ν₃ band, stronger than 2ν₆^±2, is perturbed by two resonances: a Coriolis resonance with the very weak ν₃ + ν₅ band, no line of which has been observed, and an anharmonic resonance with 2ν₆⁰, only four K subbands of which have been observed. For both isotopic species, a standard deviation of about 0.002 cm^?1 has been obtained for about 750 lines of ν₂ + ν₃ and 2ν₆⁰.     

Diode laser spectroscopy of the ν11 band of ethylene-d4

The ν₁₁ band of ethylene-d₄ was observed in a region from 2174 cm^?1 to 2227 cm^?1 with Doppler-limited resolution (about 3 × 10^?3 cm^?1) by using a diode laser spectrometer. The ^qP, ^qQ, and ^qR branches with five weak ^sQ lines were analyzed up to K_a = 12 to determine the ground-state as well as the upper-state molecular constants. A Coriolis interaction, possibly a b-type one with the ν₂ + ν₇ band, was found to perturb high-K_a lines. The discrepancy between the observed and the calculated inertia defects in ν₁₁ was explained by the interaction.     

The region of the 3ν3 band of methane

The spectrum of methane near 9000 cm^?1, the region of the 3ν₃ band, has been recorded at Meudon Observatory with a Fourier transform spectrometer under high resolution. Intensity measurements at two different temperatures, 149 and 295 K, have allowed us to identify two new vibration bands by determining the lower-state quantum numbers J of the transitions. About 100 lines are now assigned in this range, including P and Q branches. Furthermore, the first detailed rotational analysis of the 3ν₃ band has been made; nine parameters of the band have been determined. The standard deviation of the differences between observed and computed wavenumbers for 45 lines of the 3ν₃ band is only 0.045 cm^?1. It is found that the observed 45 lines of the 3ν₃ band correspond to the sublevel l₃ = 3 and C_v = F₂.     

Coherent Stokes and anti-Stokes Raman spectra of the ν1 (A1) and ν2 (E) bands of SF6 and UF6

Coherent Stokes and anti-Stokes Raman scattering are used to study the ν₁ and ν₂ spectral band profiles of UF₆ and SF₆. Most of the observed SF₆ “hot” bands are assigned, leading to evaluations of the anharmonicity constants X_ij: X₁₂ = ?(2.80 ± 0.30) cm^?1, X₁₄ = ?(1.00 ± 0.15) cm^?1, X₁₅ = ?(1.00 ± 0.15) cm^?1. For UF₆, a tentative assignment of the “hot” bands is made: X₁₂ = ?(1.80 ± 0.30) cm^?1, X₁₃ = ?(1.60 ± 0.30) cm^?1, X₁₄ = ?(0.20 ± 0.10) cm^?1, X₁₅ = ?(0.25 ± 0.10) cm^?1, and X₁₆ = ?(0.10 ± 0.05) cm^?1. Parameters such as the vibration-rotation coupling constants are determined. For SF₆: α = (7 ± 2) × 10^?5 cm^?1 for the ν₂ band and α = ?(1.02 ± 0.01) 10^?4 cm^?1 for the ν₁ band. The calculated spectral profiles of the coherent Stokes or anti-Stokes spectra, which are in good agreement with experimental results, give values for the resonant and nonresonant parts of the susceptibility in both molecules. They also show, in some cases, the influence of neighboring combination bands.     

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.     

Analysis of the ν2 + ν3 band of 12CH4 and 13CH4

The ν₂ + ν₃ bands of ¹²CH₄ and ¹³CH₄ occurring in the region 4400–4650 cm^?1 have been studied from spectra recorded with a high-resolution Fourier transform spectrometer (resolution better than 0.01 cm^?1). Champion's Hamiltonian expansion, Canad. J. Phys.55, 1802 (1977), is applied to the problem of the two interacting F₁ and F₂ vibrational sublevels of this type of a band. As the P branch of ν₂ + ν₃ is strongly overlapped by neighboring bands, a combination-difference method, adapted to tetrahedral XY₄ molecules has been developed to help assignments of lines. A fit of 700 transitions has been performed using 13 new effective constants in the case of ¹²CH₄. In the case of ¹³CH₄, 532 transitions have been fit to 18 constants. The known parameters, relative to the vibrational ground state and the ν₃ state for both methanes, and the ν₂ state for ¹²CH₄ were fixed throughout. Most of the perturbed levels, up to J′ = 12, are well reproduced and the general agreement between experimental and calculated transitions is satisfactory with standard deviations of 0.047 cm^?1 (¹²CH₄) and 0.041 cm^?1 (¹³CH₄). The results (order of magnitude of obtained (ν₂ + ν₃) parameters and comparison of observed and computed intensities) indicate that the ν₂ + ν₃ band is perturbed by many other bands.     

Helium- and argon-broadening coefficients of phosphine lines in the ν2 and ν4 bands

Pressure broadening of phosphine lines by helium and argon at room temperature has been experimentally investigated by high-resolution diode-laser spectroscopy. The broadening coefficients are measured for 38 transitions of PH₃ in the ^QR branch of the ν₂ band and in the ^PP and ^RP branches of the ν₄ band. The recorded lines with J values ranging from 3 to 14 and K from 0 to 10 are located between 1062 and 1094 cm⁻¹. The retrieval of the collisional widths is carried out by fitting each spectral line with a Voigt profile, a Rautian profile and a speed-dependent Rautian profile. The latter model provides larger broadening coefficients than the Voigt model. They are also calculated on the basis of a semiclassical model involving the atom-atom Lennard-Jones potential. The theoretical results are in reasonable agreement with the experimental data and reproduce the J and K dependencies of the broadenings.     

New infrared integrated band intensities for HC3N and extensive line list for the ν5 and ν6 bending modes

The infrared spectrum of cyanoacetylene (also called propynenitrile) has been investigated from 400 to 4000 cm⁻¹ at a resolution of 0.5 cm⁻¹. Integrated intensities of the main bands and a number of weaker bands have been obtained with an uncertainty better than 5%. Inaccurate values in previous studies have been identified in particular concerning the intensity of the strong ν₅ stretching band at 663.2 cm⁻¹. Former results on the temperature dependence of integrated intensities have also been revisited.Synthetic spectra calculation has been performed for the ν₅ and ν₆ bands on the basis of the best available high resolution data. It has been shown that the GEISA line parameters for HC₃N are not sufficient to reproduce the band intensities and some hot band features observed in our experimental spectra at room temperature. As a first step, the model spectra has been improved by including a number of missing hot subbands and by calculating accurately the hot band relative intensities. Finally, a perfect agreement between calculated and observed spectra was achieved on the basis of a global analysis of HC₃N levels up to 2000 cm⁻¹ combined with the new integrated intensity measurements. A new extensive line list for the ν₅ and ν₆ bending modes of HC₃N has been compiled.