Low temperature vibrational relaxation of OD in the A2Σ, state

The vibrational relaxation of the A ²Σ state of OD has been studied in the low translational temperature environment of an argon free-jet (T_trans near 5 K). Using laser induced fluorescence (LIF), the absolute vibrational relaxation rate coefficients were measured for OD A²Σ (ν′) to be 7.1 ± 2.6 × 10^?11, 5.9 ± 1.4 × 10^?11, and 2.7 ± 1.1 × 10^?11 cm³ s^?1 for the ν = 3, 2 and 1 states, respectively. State-to-state relaxation rate coefficients were also obtained for the ν= 1, ? = 1 level going to ν= 0, ? levels in the A²Σ manifold. The rotational relaxation rate coefficient for ν= 1, ?= 1 in the A state of OD was found to be 9.6 ± 1.0 × 10^?11cm³s^?1. These values are consistent with values measured for OH A²Σ, and the total loss rates are near the capture rate coefficient value. The vibrational relaxation rate coefficients k_ν appear to be governed by the vibrational energy of the molecule rather then by interaction with nearby dissociative states such as the a⁴Σ state. The relative Einstein A factors for the A²σ (ν = 3) state of OD were determined and compared with the available calculated value.     

High resolution infrared spectrum of the ν4 band of DCCF

The bending vibration-rotation band ν₄ of DCCF was studied. The measurements were carried out with a Fourier spectrometer at a resolution of about 0.03 cm^?1. The constants B₀=0.29141(1)cm^?1, α₄=?5.02(2)×10^?4cm^?1, q₄=4.52(3)×10^?4cm^?1, and D₀=9.2(4)×10^?8cm^?1 were derived. The rotational analysis of the “hot” bands 2ν₄(Δ) ← ν₄(II) and 2ν₄(Σ⁺) ← ν₄(II) was performed. In addition, the “hot” bands ν₄ + ν₅ ← ν₅ were assigned. A set of vibrational constants involved was derived.     

Dipolar studies in CaF2 with Ce3+

Dielectric relaxation in CaF₂ doped with various amounts of Ce³⁺ (0·01 to 1·0 mol%) was measured. The value of the activation energy for orientation of the dipoles {Ce³⁺-F^? interstitial} was determined to be H = (0·46 ± 0·01) eV. The frequency factor was found to have the value τ_o = (5 ± 1) × 10^?15 sec, giving for the vibrational frequency of the interstitial the value ν_o = (5 ± 1) × 10¹³ sec^?1.The number of dipoles contributing to the dielectric loss peak was determined to be between 10¹⁷ and 8 × 10¹⁷ cm^?3 for the different doping amounts of Ce³⁺. Optical absorption measurements showed the existence of large aggregate bands. We could verify that there exists a second-order reaction of aggregation, which is responsible for the non-linearity found between optical absorption at 305 nm and the nominal concentration of Ce³⁺ in the samples. On the other hand, if we assume that the centers which contribute to optical absorption at 305 nm are those also responsible for the relaxation peak, we find that the number contributing to each process is not the same. We can define an interaction radius R as the minimum separation between two dipoles allowing them to contribute to the relaxation peak. From our experimental data R ? 3·8 × 10^?7 cm.     

First far-infrared high-resolution analysis of the ν2 and ν4 bands of phosgene 35Cl2CO and 35Cl37ClCO

ABSTRACT

A Fourier transform spectrum of phosgene (Cl₂CO) has been recorded in the 17.3-μm spectral region at a temperature of 180 K and at a resolution of 0.00102 cm^?1 using a Bruker IFS125HR spectrometer coupled to synchrotron radiation, leading to the observation of the ν₂ and ν₄ vibrational bands of the two isotopologues ³⁵Cl₂CO and ³⁵Cl³⁷ClCO. The corresponding upper-state ro-vibrational levels were fit using a Hamiltonian model accounting for the A-type Coriolis interaction linking the rotational levels of the 2¹ and 4¹ vibrational states. In this way, it was possible to reproduce the upper-state ro-vibrational levels to within the experimental uncertainty, i.e. ～0.30 × 10^?3 cm^?1. Very accurate rotational and centrifugal distortion and interaction constants were derived from the fit, together with the following band centres: ν₀(ν_2, ³⁵Cl₂CO) = 572.526299(30) cm^?1, ν₀(ν_4, ³⁵Cl₂CO) = 582.089026(30) cm^?1, ν₀(ν_2, ³⁵Cl³⁷ClCO) = 568.951791(35) cm^?1 and ν₀(ν₄, ³⁵Cl³⁷ClCO) = 581.758279(35) cm^?1.     

Emission and excitation spectra of CCl2 in solid argon

Studies of the CCl₂ excitation spectra in solid argon give values of 624 and 304 cm^?1 for the upper-state vibrational modes ν₁ and ν₂, respectively. The 000-000 band of the electronic transition occurs at 17 092 cm^?1. Vibrational relaxation in the upper state is fast compared with the 3.6 μsec emission lifetime, and only vibrationally relaxed emission is observed.     

High resolution infrared study of the parallel band ν3 of chloroform CH35 Cl3

The infrared spectrum of chloroform in the region of the parallel fundamental band ν₃ around 367 cm^?1 has been measured with a Fourier spectrometer at a resolution of 0.001 cm^?1. An isotopically pure sample of CH³⁵Cl₃ was used. More than 5000 lines were assigned in the ν₃ band. A reanalysis of the ground state constants was performed by combining 1671 combination differences from this work, 712 differences from a previous study of the ν₂ band, and 80 millimetre wave lines from the literature. In the analysis of the ν₃ band, a model of an unperturbed symmetric top band was applied. The data were fitted with a standard deviation of 0.18 × 10^?3 cm^?1, and the following leading parameters were obtained: ν₀ = 367.295 550(8) cm^?1, B ₃—B ₀ = ?77.058(4) × 10^?6 cm^?1 and C ₃—C ₀ = ?18.600(11) × 10^?6 cm^?1. In addition, several hot bands have been studied. The isotopic effects were studied also by analysing spectra of the isotopically natural sample.     

A high resolution FTIR spectroscopic study of the hydrogen-bonded heterodimer H3N−HCN

The spectrum of the symmetric top, hydrogen-bonded heterodimer H₃N?HCN has been recorded between 2900 and 3200cm^?1 using a high resolution FTIR spectrometer. The more intense bands are associated with the ν₂ (H?CN stretch) vibration and include hot bands associated with the low frequency modes ν₅, ν₂ and ν₁₀. Weaker difference bands of the type ν₂+(n?1) ν5?nν₅ are also observed. Analysis of the bands yields values for the band origins: ν2/0=3110·5±0·2cm^?1 and ν5/0=140±5cm^?1 and the anharmonicity constants: x _2,10=12·7±0·5cm^?1, x _2,9≈x _2,5=23±3cm^?1 and x _5,10=?5±2cm^?1. The lifetime in ν₂ with respect to vibrational predissociation, estimated from the width of the sharpest observed feature, is 100?200 ps but there is some indication that this lifetime may decrease at high J.     

The two-dimensional anharmonic oscillator: The CCC bending mode of C3O2

Newly observed data on the rotational constants of carbon su?ide in excited vibrational states of the low-wavenumber bending vibration ν₇ have been successfully interpreted in terms of the two-dimensional anharmonic oscillator wavefunctions associated with this vibration. By combining these results with published infrared and Raman spectra the vibrational assignment has been extended and a refined bending potential for ν₇ has been derived: this has a minimum at a bending angle of about 24° at the central C atom, with an energy maximum at the linear configuration some 23 cm^?1 above the minimum. From similar data on the combination and hot bands of ν₇ with ν₄ (1587 cm^?1) and ν₂ (786 cm^?1) the effective ν₇ bending potential has also been determined in the one-quantum excited states of ν₄ and ν₂. The effective ν₇ potential shows significant changes from the ground vibrational state; the central hump in the ν₇ potential surface is increased to about 50 cm^?1 in the v₄ = 1 state, and decreased to about 1 cm^?1 in the v₂ = 1 state. In the light of these results vibrational assignments are suggested for most of the observed bands in the infrared and Raman spectra of C₃O₂.     

Charge carrier mobility in crystals of the Pb<Subscript>0.67</Subscript>Cd<Subscript>0.33</Subscript>F<Subscript>2</Subscript> superionic conductor

The frequency (ν = 10^?1–10⁷ Hz) dependences σ(ν) of the conductivity of single crystals of the Pb_0.67Cd_0.33F₂ superionic conductor with the fluorite-type structure (CaF₂) in the temperature range of 132–395 K have been studied. The dependences σ(ν) have been discussed in the framework of the hopping relaxation of ionic carriers, which are mobile anions F^?. From experimental curves σ(ν), the direct-current (dc) conductivity σ_dc and the average charge carrier hopping frequency ν_h have been determined. This has made it possible to calculate the charge carrier mobility μ_mob and charge carrier concentration n _mob in these crystals. At room temperature (293 K), the electrical parameters are σ_dc = 1.6 × 10^?4 S/cm, ν_h = 2.7 × 10⁷ Hz, μ_mob = 2.0 × 10^?7 cm²/(s V), and n _mob = 5.1 × 10²¹ cm^?3.     

High-resolution analysis of the ν1 and ν5 bands of phosgene 35Cl2CO and 35Cl37ClCO

Fourier transform spectra of phosgene (Cl₂CO) have been recorded in the 11.75 and 5.47 μm spectral regions using a Bruker IFS125HR spectrometer at resolutions of 0.00102 and 0.0015 cm^?1, respectively, leading to the observation of the ν₅ and ν₁ vibrational bands of the two isotopologues ³⁵Cl₂CO and ³⁵Cl³⁷ClCO. The corresponding upper state ro-vibrational levels were fit using Watson-type Hamiltonians and/or a Hamiltonian matrix accounting for resonance effects when necessary. In this way, it was possible to reproduce the upper state ro-vibrational levels to within the experimental accuracy, i.e. ～0.17 × 10^?3 cm^?1. Very accurate rotational and centrifugal distortion constants were derived from the fit together with the following band centres: ν₀(ν_5, ³⁵Cl₂CO) = 851.012737(20) cm^?1, ν₀(ν_5, ³⁵Cl³⁷ClCO) = 849.995451(90) cm^?1, ν₀(ν_{2 +} ν_3, ³⁵Cl³⁷ClCO) = 864.42370(50) cm^?1, ν₀(ν_1, ³⁵Cl₂CO) = 1828.202514(40) cm^?1 and ν₀(ν_1, ³⁵Cl³⁷ClCO) = 1827.246444(20) cm^?1.     

Influence of pressure on the relative population of the two lowest vibrational levels of the C <Superscript>3</Superscript> Π<Subscript>u</Subscript> state of nitrogen for electron beam excitation

Continuous and pulsed 12 keV electron beams were used to excite nitrogen within a gas cell at pressures ranging from 10 to 1400 hPa. The pressure dependence of the ratio of photon fluxes for emission from vibrational levels v'=0 and 1 of the C ³Π _u state has been studied. The results confirm the presence of a collisional excitation mechanism populating v'=0, 1 in addition to electron impact excitation. Rate constants of (1.27 ±0.04)×10^-11 cm³s^-1 [ v'=0] and (2.68 ±0.08)×10^-11 cm³s^-1 [ v'=1] were measured for C ³Π _u quenching by ground state nitrogen. For electron beam conditions relative excitation efficiencies of 1:0.59:0.22 for vibrational levels 0, 1 and 2 were calculated. The recorded flux ratios are compared with the predictions given by a vibrational relaxation model.     

A Vibrational Spectroscopic Study of the So-Called Healing Mineral Papagoite CaCuAlSi2O6(OH)3

ABSTRACT

Papagoite is a silicate mineral named after an American Indian tribe and was used as a healing mineral. Papagoite CaCuAlSi₂O₆(OH)₃ is a hydroxy mixed anion compound with both silicate and hydroxyl anions in the formula. The structural characterization of the mineral papagoite remains incomplete. Papagoite is a four-membered ring silicate with Cu²⁺ in square planar coordination.

The intense sharp Raman band at 1053 cm^?1 is assigned to the ν₁ (A _1g) symmetric stretching vibration of the SiO₄ units. The splitting of the ν₃ vibrational mode offers support to the concept that the SiO₄ tetrahedron in papagoite is strongly distorted. A very intense Raman band observed at 630 cm^?1 with a shoulder at 644 cm^?1 is assigned to the ν₄ vibrational modes.

Intense Raman bands at 419 and 460 cm^?1 are attributed to the ν₂ bending modes.

Intense Raman bands at 3545 and 3573 cm^?1 are assigned to the stretching vibrations of the OH units. Low-intensity Raman bands at 3368 and 3453 cm^?1 are assigned to water stretching modes. It is suggested that the formula of papagoite is more likely to be CaCuAlSi₂O₆(OH)₃ · xH₂O. Hence, vibrational spectroscopy has been used to characterize the molecular structure of papagoite.     

Torsional tunneling splittings in the v4 = 1 excited torsional state of Si2H6: analysis of hot bands accompanying fundamental transitions in the high resolution infrared spectrum

The (ν₄?+?ν₆)???ν₄, (ν₄?+?ν₈)???ν₄ and (ν₄?+?ν₉)???ν₄ hot infrared systems of disilane (Si₂H₆) have been analysed at high resolution, and the values of the relative vibration–rotation–torsion parameters have been determined. The torsional splitting is about 0.500?cm^?1 in the ν₄ and ν₄?+?ν₆ states, and decreases strongly in the vibrationally degenerate upper states ν₄?+?ν₈ (about 0.0272?cm^?1 on average) and ν₄?+?ν₉ (about 0.3019?cm^?1), consistent with theoretical predictions. Comparison between the vibrational wavenumbers of cold transitions and hot transitions originating in the excited torsional state v₄?=?1 allows one to determine the change of the fundamental torsional frequency ν₄ caused by the excitation of small amplitude vibrations. A remarkable increase in ν₄ of about 8.599?cm^?1 is found in the v₉?=?1 state (E_1d SiH₃-rocking mode, asymmetric to inversion in the staggered geometry), and this corresponds to an increase in the torsional barrier height in this excited fundamental vibrational state by about 48.77?cm^?1. The mechanism responsible for the decrease of the torsional splittings in the degenerate vibrational states is briefly outlined by means of second-order perturbation theory, using torsion-hindered vibrational basis functions of E_1d and E_2d symmetries for the degenerate modes.     

Simultaneous Analysis of Rovibrational and Rotational Spectra of thev5= 1 andv8= 1 Vibrational Levels of Propyne

The microwave and submillimeter wave spectra of propyne between 17 and 358 GHz were measured and the rotational transitions in thev₈= 1 excited vibrational state of the CH₃rocking vibration were assigned. About 1050 wavenumbers of the ν₈vibration–rotation fundamental band and about 600 wavenumbers of the ν₅fundamental band of the[formula]stretching vibration were assigned from the infrared spectrum between 910 and 1130 cm⁻¹which was used previously (G. Graneret al., J. Mol. Spectrosc.161,80–101 (1993)) in the analysis of the combinationv₉=v₁₀= 1 and thev₁₀= 3 overtone levels (ν₉being the[formula]bending and ν₁₀the[formula]bending vibrations). The rovibrational and rotational data corresponding to the two fundamental levels were analyzed simultaneously in least-squares fits using a model which treats together all the vibrational levels in the region around 1000 cm⁻¹with their strong anharmonic and vibration–rotation resonances. The refined parameters reproduce the infrared and submillimeter wave data of thev₅= 1 level with standard deviations of 0.32 × 10⁻³cm⁻¹and 59 kHz, respectively, while for thev₈= 1 level the standard deviations were 0.41 × 10⁻³cm and 290 kHz. The refined parameters of the combination and overtone levels provide reliable predictions for future submillimeter wave studies.     

The ν6, ν8 3ν4+ν12 infrared system of Si2H6 under high resolution: rotational and torsional analysis

A Fourier transform infrared spectrum of disilane has been measured at a Doppler limited resolution, and analysed in the region of the ν₆ and ν₈ fundamentals, from about 800 to 1020cm^?1. The torsional splittings are not resolved in the ν₆ band, showing that the splittings in the ν₆ = 1 state and in the ground state are almost identical. The torsional splittings in the reasonably unperturbed regions of the ν₈ fundamental are about 0.0146cm^?1, and a detailed rotation-torsion analysis shows that the intrinsic splittings in the ν₈ = 1 state are smaller than in the ground state by this amount. An intrinsic torsional splitting about 0.0150 cm^?1 is estimated in the vibrational ground state and in the ν₆ = 1 state, and almost vanishing in the ν₈ = 1 state (about 0.0004cm^?1), with a barrier height around 407cm^?1. This is in agreement with the expectation from theory. The ν₈ band, beyond a moderate x, y-Coriolis coupling with ν₆, is affected by several perturbations, also selective in the torsional components. The 3ν₄ + v¹² combination, with three quanta of the torsional mode excited and large torsional splittings, is the main perturber, causing both Fermi and Coriolis resonances in several regions of the spectrum. The vibrational origins of all four torsional components of 3ν₄ + v¹² were determined. Other perturbative effects are attributed to the systems 2ν₃ + ν₄, and ν₄ + 24₉(E + A). The spectrum was numerically analysed, and the relevant vibration-rotation-torsion parameters were determined.     

Concentration quenched luminescence and energy transfer analysis of Nd3+ ion doped Ba-Al-metaphosphate laser glasses

This paper reports the dopant ion (Nd³⁺) concentration effects on its luminescence properties in a new glass system based on barium-alumino-metaphosphates. Amongst the studied concentrations range of 0.276–13.31×10²⁰ ions/cm³, the glass with 2.879×10²⁰ ions/cm³ (1 mol%) Nd³⁺ concentration shows intense NIR emission from ⁴F_3/2 excited state, followed by a decrease in emission intensity for further increase in Nd³⁺ ion concentration. The observed luminescence quenching is ascribed to Nd³⁺ self-quenching through the donor-donor migration assisted cross-relaxation mechanism. The microscopic energy transfer parameters for donor-acceptor energy transfer, C _DA, and donor-donor energy migration, C _DD, have been obtained from the theoretical fittings to experimental decay curves and the spectral overlap model respectively. The C _DD parameters (×10^?39 cm⁶/sec) are found to be about three orders greater than that of C _DA (×10^?42 cm⁶/sec) for Nd³⁺ self-quenching in this host, demonstrating that the excitation energy migration among donors is due to the hopping mechanism. The energy transfer micoparameters obtained in the present study are comparable to the values reported for commercially available laser glasses LHG-8 and Q-98.     

High resolution IR spectrum of the ν8 band of CH2DF: analysis of the interactions with the near vibrational levels

The IR spectrum of the ν₈ band of monodeutero methyl fluoride has been recorded with a resolution of 0.004 cm^?1 using a Fourier transform spectrometer. The ν₈ vibration, of A′′ symmetry species, gives rise to a pure c-type envelope centred at 1298.58 cm^?1, resembling a perpendicular band of a prolate symmetric rotor. From the spectral analysis it has been found that ν₈ is coupled with ν₄ for the low K_a sublevels while for the higher ones other vibrational states, directly or indirectly, are also interacting. For satisfactory reproduction of the rovibrational data of ν₈, the Watson's Hamiltonian in the I^r representation has been implemented with interaction parameters, which included first- and second-order a-, b-type and c-type Coriolis couplings with ν₄ and ν₉, respectively. Being these states also interacting with other levels, the effective spectroscopic parameters of the analysed band up to fourth order have been obtained from a data set formed by the six fundamentals located below 1500 cm^?1.     

基于沉淀工艺制作四脚氧化锌纳米材料场致发射阴极的研究

采用沉淀法制备四脚氧化锌纳米材料场致发射阴极,将阴极和荧光屏封装起来抽真空并对屏施加电压,测试阴极的发射电流和荧光屏的发光亮度.利用沉淀法制备出面积为(13×15) cm²的阴极,测试结果表明,硅酸钾体积百分比在50×10^-3—83×10^-3范围,硝酸钡浓度在50×10^-4—77×10^-4 M范围,四脚氧化锌的浓度在82×10^-4—12×10^{-3关键词： 场致发射 沉淀法 显示屏亮度}     

High-resolution infrared spectroscopy of CH2D79Br: ro-vibrational analysis of the ν4 and ν8 fundamental bands

The high-resolution Fourier transform infrared spectrum of CH₂D⁷⁹Br has been recorded and analysed in the region of the ν₄ and ν₈ fundamentals located in the range 1125?1360 cm^?1. The strong ν₄ band, centred at 1225 cm^?1, shows an a/b-hybrid structure with predominant a-type character, whereas ν₈, at 1253 cm^?1, generates a c-type contour comparable in intensity to the b-type component of ν₄. The upper states of these fundamentals are coupled through a- and b-type Coriolis resonances; further complications in this band system arise from perturbations due to the ν₆ = 2 (1183 cm^?1) and ν₅ = ν₆ = 1 (1359 cm^?1) dark states. The former interacts with ν₈ = 1 by b-type Coriolis coupling, whereas the latter perturbs the ν₄ = 1 and ν₈ = 1 levels by anharmonic and a-type Coriolis resonances, respectively. Accurate upper state parameters and interaction terms have been determined for the tetrad system ν₄/ν₈/2ν₆/ν₅+ν₆ by also including in the dataset the assigned transitions of the 2ν₆?ν₆ and ν₅+ν₆?ν₆ hot bands obtained from previous analysis.