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1.
The dipole moment of D2O has been determined from Stark effect measurements for the 313–220 and 441–532 microwave transitions as 1·857 ± 0·006 and 1·869 ± 0·005D respectively. A rotational dependence of dipole moment has also been established for HDO through μa in the 220–221 and 532–533 transitions; μa was determined as 0·662 ± 0·001 and 0·644 ± 0·001D respectively. The total dipole moment for HDO has been determined from the 321–414 transition to be 1·85 ± 0·01D and to lie within 0·1° of the bisector of the HOD angle. High resolution Stark spectroscopy has been performed on the 624–615 transition of D2O with improved precision using the 337 μm emission line of the HCN laser. This experiment has confirmed the dipole results from the microwave work and the frequency of the 624–615 transition in D2O has been determined as 890 395 ± 3 MHz.

The slight increase of dipole moment with deuteration is consistent with the dipole moment for H2O determined from the dielectric constant. This increase is discussed for the vibrational ground state (as for ammonia) in terms of anharmonicity in the bending vibration. The change of μ with rotational transition is interpreted in terms of large changes in molecular geometry for certain rotational states due to centrifugal distortion.  相似文献   

2.
The condensed isotopic modifications of methane, CH4, CH2D2, and CD4 and their solutions with Kr were investigated using dielectric techniques. The polarizabilities were computed from the permittivities of the pure liquids. Phase diagrams of methane-krypton alloys were deduced in the liquid-solid coexistence region and for the low temperature phases (T<30 K). From the Curielaws, which described the permittivities of the (Kr)1-x(CH2D2)x mixed crystals, the permanent dioole moment of CH2D2 is calculated to be 4 mD. In the octopolar ordered phases of the solid solutions the effective dipole moments are enhanced significantly.  相似文献   

3.
The anharmonic force field of methane has been refined to fit spectroscopic data from the isotopic species 12CH4, 13CH4, 12CH4, 12CH3D, 12CHD3 and 12CH2D2. Six of the thirteen cubic force constants have been determined experimentally, the remaining cubic constants being fixed at values derived from ab initio calculations. The quartic force field is very crude, in that only frrrr has been refined. It is concluded however that the cubic and quartic force fields, even though they are subject to limitations, provide a considerable improvement in the experimental determination of the r e structure and the quadratic force field. The equilibrium bond length is found to be r e(CH) = 1·0858 ± 0·001 Å.  相似文献   

4.
As a tetrahedral molecule, methane has no permanent dipole moment. Its spectrum, however, displays faint absorption lines in the THz region, due to centrifugal distorsion effects. This is important for planetary applications since this region is used to measure methane concentration in some planetary atmospheres, in particular on Titan. Up to now, all measurements relied either on some old low resolution infrared absorption spectra, or on high resolution Stark measurements for low J values only. Even if these results have been reexamined recently [Wishnow EH, Orton GS, Ozier I, Gush HP. The distorsion dipole rotational spectrum of CH4: a low temperature far-infrared study. J Quant Spectrosc Radiat Transfer 2007;103:102-17], it seemed highly desirable to obtain much more precise laboratory data.The high-intensity synchrotron radiation, combined with a 151.75±0.1 m optical path in a White cell and a Bruker IFS 125 HR FTIR spectrometer at the AILES beamline of SOLEIL, enabled us to record this very weak spectrum at high resolution for the first time. Spectra were obtained in the 50-500 cm−1 wavenumber range at 296 K and 9.91, 20, 50 and 100 mbar with a resolution of 0.00074, 0.00134, 0.0034 and 0.0067 cm−1 (FWHM of the sinc function), respectively. The rotational clusters are fully resolved and the good signal-to-noise ratio has enabled precise measurements of transition intensities (92 cold band lines and 96 Dyad-Dyad hot band lines, with normal abundance intensities in the range 2×10−26-1×10−24 cm−1/(mol cm−2)), yielding an accurate determination of the dipole moment derivatives. Such results should allow a better determination of CH4 concentration in planetary objects.  相似文献   

5.
Ab initio calculations of harmonic force constants and dipole moment derivatives have been performed for the diatomic molecules LiH, Li2 and BH, using Hartree-Fock perturbation theory for a series of spherical gaussian SCF-MO wavefunctions. The results of these computations support the conclusion made in a previous paper that the so-called general method of calculation is the most reliable. The results obtained with the energetically best wavefunctions are (experimental values in parentheses, atomic units throughout): Force constants: LiH 0·071 (0·066); Li2 0·019 (0·016); BH 0·210 (0·196). Dipole moment derivatives: LiH - 0·48 (-0·42±0·06); BH - 0·67 (-0·4).  相似文献   

6.
The ENDOR spectrum of 13C substituted (carbonyl carbon) triplet excited benzophenone was studied at ca. 100 G applied magnetic field by means of optical detection. The benzophenone was substitutionally dissolved in dibromodiphenylether (DDE). The ENDOR transitions and the E.P.R. transitions were studied as a function of applied field direction in the ab and bc crystal planes. The angle ? between the line joining the phenyl group centres and a principal axis of the fine structure tensor was found to be 23·6° ± 0·02° (standard deviation limited to one set of measurements). The principal axes of the 13C hyperfine tensor were within experimental error (±10°) coincident with the fine structure axes. The principal values of the hyperfine tensor were found to be : |Axx /h| = 43·16 ± 1·84, |Ayy /th| = 22·66 ± 2·50, |Azz /h| = 10·25 ± 1·30 MHz. The low-field ENDOR does not provide an indication of the signs of these tensor elements, so the value of the isotropic coupling constant cannot be measured. Two values of the anisotropic (dipole) hyperfine tensor elements were deduced on the assumption that the transitions frequencies are mainly determined by interactions between the nuclear spin and electron density on the carbonyl carbon atom. These values were (i) A xx / d /h = 17·82, Ayy /h = -22·68, Azz /h = -15·14 MHz and (ii) Axx /h = 39·73, Ayy /h = -26·09, Azz /h = -13·63 MHz. Set (ii) is consistent with recent calculations of the spin density distribution in triplet benzophenone in which the orbital spin densities are 0·64 for the carbonyl carbon π-orbital, 0·17 for the oxygen π-orbital, and 0·88 for the non-bonding orbital on oxygen (all expressed as fractions of one electron).

Isotope effects on the fine structure constants of triplet benzophenone were measured and found to be consistent with the changes occurring in the spin-orbit coupling with the ground state.

The kinetic parameters for the excitation and de-excitation of the triplet substates were deduced from transient ODMR studies of benzophenone in DDE. The Tz spin state is mainly populated (85–88 per cent) and this is also the most strongly radiative state (kz r = 0·88). The steady-state populations of the three triplet levels are similar.  相似文献   

7.
General expressions for the radial wavefunctions and the rotationless matrix elements of the dipole moment for the transitions 0→0 to 0→4 are obtained using a fifth-power internuclear potential, a quartic dipole moment function, and third-order perturbation theory. Line intensities in the 0→2 and 0→3 bands of CO have been measured for pressures varying from 2 to 5 atm. Using the values of the vibrational transition moments |R02| and |R03| deduced from our measurements and the values of |R00|, |R01| and |R04| previously given, we evaluate the coefficients M0 to M4 of the dipole-moment function for CO.  相似文献   

8.
The phosphorescence spectrum of the metastable 4 Eu state of copper porphin in single crystals of n-octane (C8) and n-decane (C10) has been studied between 2·3 and 35 K, with and without a magnetic field B. The crystal field splitting between the orbital components observed at 35 K is δ = 30·3 ± 0·3 (C8), 13·8 ± 0·2 cm-1 (C10). From the Zeeman shifts we derive the effective orbital angular momentum Λ′ = 0·8 ± 0·2 (C10), the spin-orbit coupling parameter |Z′| = 1·5 ± 1·0 cm-1 (C10), the spin-spin dipolar interaction parameters D = -0·1 ± 0·2 cm-1 (C8, C10) and |E| = 0·31 ± 0·03 cm-1 (C8, C10), and the g-factors g = 2·14 ± 0·04 (C8, C10) and g = 2·00 ± 0·03 (C8, C10).  相似文献   

9.
Theoretical calculations of the neutron electric dipole moment Dn are reviewed for various theories of CP violation. It is shown that for the superweak interaction theory Dn is less than 10?29e · cm in contrast to values of 10?23 to 10?24 predicted by many but not all milliweak theories. It is concluded that prospective measurements of Dn may provide decisive evidence against or significant evidence in favour of the superweak theory.  相似文献   

10.
From thirty-nine combination difference equations we have determined three significant ground-vibronic state constants of silane: β 0/hc=2·85941 cm-1, γ 0/hc=-3·82×10-5 cm-1 and ε 0/hc=-7·97×10-7 cm-1 or in Hecht's notation B 0=2·85941 cm-1, D s=3·82×10-5 cm-1 and D t=2·436×10-6 cm-1.  相似文献   

11.
Extended and minimal basis set ab-initio valence-bond (VB) calculations have been performed for the following molecules: LiH, CH, 1CH2, 3CH2, CH3, NH3 and H2O. The influence of the choice of the basis sets and of the structures included on the values of a few observables, including energy, geometry, hyperfine coupling constants and dipole moment, has been studied.  相似文献   

12.
The I.R. spectrum of the ν3 band (4·5 µm) of N2O has been studied for temperatures varying from 219 to 298 K and densities up to 85 kg m-3. The 2v 3 band (2·3 µm) has been analysed at room temperature for densities up to 182 kg m-3; measurements of the integrated intensities as a function of density show no evidence of pressure induced absorption. This band has also been observed in the vicinity of the critical region.

The dipole moment autocorrelation function is used to assess a collisional model derived from the impact approximation and the Gordon M- and J-diffusion models developed classically as well as the semi-classical M-diffusion model. The M- and J-diffusion models reproduce well the experimental correlation function for the 3 band; the semi-classical M-diffusion model is better than the classical ones for the overtone 2v 3 and gives a satisfactory account of the correlation functions. For the collisional model considered which implies uncorrelated rotational levels, a discrepancy between theoretical and experimental correlation functions and bandshapes becomes noticeable from about 40 kg m-3 and increases with density.  相似文献   

13.
S N Bhatia 《Pramana》1982,18(3):249-259
Heat capacity of MnBr2·4H2O has been measured in the critical region around the Neel temperature. The data can be fitted, over a restricted range of |t|⩽10−2, to the asymptotic power law. The critical exponents and the amplitudesA andA′ are not consistent with any theoretic predictions. However when scaling constraints are imposed, their values agree with the parameters of Ising model. Corrections to scaling are necessary to extend the range of the fit to |t|>10−2. The correction terms are asymmetric giving −1·15±0·25 as the ratio of the amplitudes of the lowest order correction terms,D andD′ above and belowT c. This value is in agreement with the recent predictions of the renormalisation group theory.  相似文献   

14.
Relative and absolute line intensities for the ν3 bands of the 12C and 13C isotopic varieties of methane have been measured using a tunable difference-frequency laser spectrometer. From these data the integrated band strength of 13CH4 is calculated to be 0.983 ± 0.007 that of 12CH4, with the uncertainty representing three standard deviations. The absolute ν3 bandstrength for 12CH4 is 266.1 ± 3.0 cm?2 atm ?1 at 294.7 K where the errors are dominated by the pressure measurement. This band strength corresponds to an effective transition moment 〈μ3〉 = 0.0534(3)D for 12CH4 from which the ν4 band dipole moment and the Herman-Wallis F factor can be estimated using a recent force field model for methane.  相似文献   

15.
ABSTRACT

The structures, stability, and vibrational spectra of the binary complexes formed between acetone and nitrous (trans and cis) acid have been investigated using ab initio calculations at the SCF and MP2 levels and B3LYP calculations with 6-311++G(d,p) basis set. Full geometry optimization was made for the complexes studied. It was established that the complex (CH3)2CO···HONO-trans is more stable than the complex (CH3)2CO···HONO-cis by 0.5–0.8 kcal·mol?1. The accuracy of the calculations has been estimated by comparison between the predicted values of the vibrational characteristics (vibrational frequencies and infrared intensities) and the available experimental data. It was established, that the methods, used in this study are well adapted to the problem under examination. The predicted values with the B3LYP/6-311++G(d,p) calculations are very near to the results, obtained with MP2/6-311++G(d,p). The calculated frequency shift Δν(O[sbnd]H) for the complex (CH3)2CO···HONO-trans (1A) is larger than for the complex (CH3)2CO···HONO-cis (1B). In the same time the intensity of this vibration increases dramatically upon hydrogen bonding. The calculated increase for the complex 1A is up to 15 times and for the complex 1B is up to 30 times. The changes in the vibrational characteristics (vibrational frequencies and infrared intensities) of (CH3)2CO upon the complexation are more insignificant than the changes in the vibrational characteristics of HONO-trans and HONO-cis.  相似文献   

16.
The nuclear magnetic shielding, electric dipole moment and electric field gradient at the nuclei were studied by ab initio computations as a function of the one-dimensional proton transfer coordinate in BrH ··· NH3. The properties are vibrationally averaged along this reaction coordinate for BrH ··· NH3 and BrD ··· NH3. The effect of a matrix has been approximated, as in previous calculations, by surrounding BrH ··· NH3 with three argon atoms.  相似文献   

17.
Multiconfiguration self-consistent-field calculation has yielded the dipole moment function for the X1Σ+ state of HI, which qualitatively confirms the experimental finding that the dipole derivative at Re is negative. The calculated dipole moment for the v = 0 vibrational level is 0.665 D for both HI and DI as compared with the experimental values of 0.38 and 0.445 ± 0.02 D, respectively. The calculated potential curve yields values of Re, D0, and ΔGv+1/2, in good agreement with spectroscopic data. A simple valence bond explanation has been provided for the qualitative difference between the dipole moment function of HI and those of the smaller hydrogen halides.  相似文献   

18.
The pure rotational R-branch spectrum of CH4 arising from the centrifugal distortion moment has been studied using a simple 12.10-m light-pipe cell and a conventional interferometer. Ten forbidden (JJ + 1) transitions for J = 7 to J = 16 have been observed in the spectral region 80–200 cm?1 with a theoretical resolution of 0.5 cm?1. The integrated intensity of the six strongest lines has been measured and was found to be of the order of twice that calculated from the distortion moment obtained earlier from a molecular beam study of the (J = 2) rotational level. In the approximation that frequency shifts due to this excess intensity are neglible, it has been determined that the rotational constant B0 = (5.245 ± 0.004) cm?1 and the scalar distortion constant DS = (1.19 ± 0.09) × 10?4 cm?1. It is argued that the excess intensity is due to higher-order terms in the dipole moment operator and the validity of the frequency analysis is considered in this context.  相似文献   

19.
The collision-induced enhancement absorption spectra of deuterium in its fundamental region in D2He at 77, 195, and 273 K and in D2Ne at 77, 195, 273, and 298 K have been recorded with an absorption path length of 26 cm for gas densities up to 670 amagat for several base densities of deuterium. At each experimental temperature, binary and ternary absorption coefficients for the fundamental band were derived from the measured integrated intensities. The theory of the “exponential-4” model for the induced dipole moment of the colliding pair of molecules was applied to the binary absorption coefficients. The overlap parts of these coefficients were obtained by subtracting the calculated quadrupolar parts from the experimental values. The magnitude parameter λ, and the range ?, of the overlap part of the induced dipole moment, were determined for the colliding molecular pairs D2He and D2Ne by obtaining the best fit of the calculated overlap part of the binary absorption coefficients as a function of temperature to the experimental values of the overlap part. Derived parameters λ, ?, and the overlap induced dipole moment μ(σ) (at the Lennard-Jones intermolecular diameter σ) for D2He and D2Ne are as follows.
  相似文献   

20.
The proton magnetic resonance second moment and spin-lattice relaxation data are reported for the two solids namely pure diethylamine and diethylamine clathrate deuterate, over the temperature range 77 K to 270 K. The results indicate that in both materials the only motion which occurs at a rate great enough to affect the N.M.R. observables is methyl group reorientation and for such motion activation energies of (2·90±0·02) kcal mole-1 and (2·34±0·02) kcal mole-1 are obtained for pure diethylamine, and the deuterate, respectively. The strength of the dipolar interaction in the deuterate as estimated from both the second moment and the maximum in the temperature dependence of nuclear relaxation rate is consistent with a carbon-proton distance of 1·10 Å and a large degree of chemical exchange of the amine protons with the deuterons of D2O.  相似文献   

Mixtureλ?μ(σ)
D2He4.7 × 10?30.24 Å2.55 × 10?2 ea0
D2Ne8.5 × 10?30.26 Å4.56 × 10?2 ea0
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