The permanent electric dipole moment of calcium monodeuteride

The sub-Doppler laser induced fluorescence spectra of numerous branch features in the B 2Sigma+ -X 2Sigma+(0,0) band of calcium monodeuteride were recorded field-free and in the presence of a static electric field of up to 7 kV/cm. The field-free spectra were analyzed to produce an improved set of fine structure parameters for the B 2Sigma+(v=0) state. The observed electric field induced splittings and shifts were analyzed to produce permanent electric dipole moments of 2.57(3) and 2.51(3) D for B 2Sigma+(v=0) and X 2Sigma+(v=0) states, respectively. The permanent electric dipole moment for the X 2Sigma+(v=0) state of CaH is estimated to be 2.53(3) D.     

Theoretical investigation of the low-lying electronic states of the alkaline hydride BeH2+ ion: Potential energy curves, spectroscopic constants, vibrational levels, and transition dipole functions

The structure and spectroscopic properties of the alkaline hydride BeH²⁺ ion have been investigated using an ab initio approach based on nonempirical pseudopotentials and parameterized l-dependent polarization potentials. The adiabatic potential energy curves and their spectroscopic constants for the ground and seventeen excited electronic states, dissociating into Be⁺(2s, 2p, 3s, 3p, 3d, 4s, 4p, and 4d) + H⁺ and Be²⁺ + H(1s and n = 2), of ²??⁺, ²??, and ²?? symmetries have been determined. As no experimental data are available, our results are discussed and compared with the few existing theoretical calculations. A very good agreement has been found with the previous theoretical data for the ground state; however many potential energy curves for the higher excited states are presented here, for the first time. Numerous avoided crossings between electronic states for ²??⁺ and ²?? symmetries have been localized and analyzed. Their existence is related to the interaction between the electronic states and to the charge transfer process between the two ionic systems Be²⁺H and Be⁺H⁺. In addition, we have calculated the vibrational energy level spacings of the bound electronic states. Furthermore, the adiabatic transition dipole functions from the X ²??⁺ and 2²??⁺ states to the higher excited states of ²??⁺ and ²?? symmetries have been evaluated and compared with the available theoretical work. This study represents the necessary initial step towards the investigation of the charge transfer processes in collision between Be⁺-H⁺ and Be²⁺-H.     

Calculations of force constants and dipole moment derivatives in silane

Force constants and dipole moment derivatives were calculated for the symmetric stretching and asymmetric stretching and bending vibrational modes for the silane molecule. The orbital exponents of small basis sets of Slater orbitals were optimized for silane in several geometrical configurations. It was determined that the addition of d orbitals to the silicon basis set has negligible effect on the calculated properties.     

Theoretical investigation for spectroscopic constants of ground-state alkaline-earth dimers with high accuracy

In this work, we provide highly accurate theoretical estimates for spectroscopic constants of the ground-state alkaline-earth dimers (Ca₂, Sr₂, and Ba₂). Electron correlation energies are calculated with coupled-cluster method at the single, double, and noniterative triple excitations [CCSD(T)] level, and the effects of full triples as well as quadruple excitations are also taken into account at the CCSDT and the CCSDT(Q) level. Our results demonstrate that high-order electron correlation is important to achieve results with high accuracy. We also find that results for Ca₂ with counterpoise corrections, which are designed to eliminate the basis set superposition error, deviate further away from those at the complete basis set limit than the uncorrected ones. The calculated binding energies and equilibrium bond lengths for Ca₂ and Sr₂ are in excellent agreement with recent experimental data. On the other hand, our results for Ba₂ are quite different from previous theoretical data, and there is no available experimental equilibrium bond length and binding energy for calibration. Based on the performance of the adopted approach for Ca₂ and Sr₂, our results should be more reliable and could be helpful for future investigations.     

Microwave spectrum,rotational constants and dipole moment of s-cis acrolein

The microwave spectrum of a second conformer of acrolein is reported for the first time. Ground-state rotational constants and quartic centrifugal distortion constants were determined from 42 transitions in the range 8–60 CHz. The small inertial defect establishes its planarity. The dipole moment of s-cis acrolein is μ_a = 2.010(5) D, μ_b = 1.573(3) D and μ_total = 2.552(3) D.     

Communication: The permanent electric dipole moment of thorium monoxide, ThO

The optical Stark spectrum of the E(0(+)) - X(1)Σ(+) (1,0) band of thorium monoxide, ThO, was recorded and analyzed to determine the permanent electric dipole moments, μ, for the E(0(+)) (v = 1) and X(1)Σ(+) (v = 0) states. Values of 2.782 ± 0.012 D (X) and 3.534 ± 0.010 D (E) were obtained. The uncertainties are 2σ statistical error. The systematic errors are estimated to be less than 1%. The experimental results are used to access the quality of electronic structure calculations of the properties of the X(1)Σ(+) (v = 0) state.     

Microwave spectrum,centrifugal distortion constants,dipole moment and quadrupole coupling constants of pentafluoropyridine

Pentafluoropyridine has been analysed in the frequency range of 8 to 18 GHz at dry ice temperature, using a conventional 100 kHz Stark modulated microwave spectrometer. The rotational constants and centrifugal distortion constants are A = 1481.539 ± 0.003 MHz, B = 1075.348 ± 0.004 MHz and C = 623.101 ± 0.001 MHz; and d_J = ?0.39 ± 0.06 kHz, d_JK = 1.86 ± 0.27 kHz, d_K = 0.70 ± 0.1 kHz, d_EJ = (0.3 ± 0.03) × 10^?6 and d_EK = (?1.5 ± 0.2) × 10^?6. The electric dipole moment has been found to be 0.98 ± 0.08 D and the values of the quadrupole coupling constants are x_aa = 1.94 ± 0.22 MHz, x_bb = ?4.08 ± 0.06 MHz and x_cc = 2.14 ± 0.22 MHz. A simple analysis based on Townes and Dailey theory points to a considerable increase in the π-electron density and excess charge on the nitrogen site.     

The permanent dipole moment of gas-phase para-amino benzoic acid revisited

The permanent dipole moment of para-amino benzoic acid has been calculated at various theoretical levels, including Hartree-Fock, second-order M?ller-Plesset perturbation (MP2), coupled cluster singles and doubles (CCSD), and triples corrections CCSD(T), and hybrid density functional theory at B3LYP level. It is found that the B3LYP method fails to provide correct results for the geometry and the permanent dipole moment. These results are significantly improved by MP2 calculations. Our best estimated dipole moments obtained at CCSD and CCSD(T) levels are in good agreement with experiment.     

The permanent electric dipole moment of chromium monodeuteride, CrD

A number of low-N lines of the X (6)Sigma(+)<--A (6)Sigma(+)(0,0) band of chromium monodeuteride, CrD, have been recorded at near the natural linewidth limit by high resolution laser excitation spectroscopy of a supersonic molecular beam sample. The shifts and splitting of these lines caused by a static electric field have been analyzed to give the permanent electric dipole moments of the X (6)Sigma(+)(upsilon=0) and A (6)Sigma(+)(upsilon=0) states as 3.510(33) and 1.153(3) D, respectively. The dipole moment of the A (6)Sigma(+)(upsilon=0) state can be measured with higher precision because of some interesting near degeneracies in its level structure. The trends in the observed dipole moments for the first-row transition metal monohydrides are rationalized and compared with theoretical predictions.     

The permanent electric dipole moment and hyperfine interactions in platinum monofluoride, PtF

The [11.9]Ω = 3∕2 ← X (2)Π(3∕2)(0,0) and (1,0) bands of platinum monofluoride, PtF, have been recorded field-free and in the presence of a static electric field. The (19)F(I = 1∕2) and (195)Pt(I = 1∕2) magnetic hyperfine interactions have been analyzed and compared with predicted values obtained using atomic information and a proposed molecular orbital correlation diagram. The optical Stark shifts were analyzed to produce the permanent electric dipole moments, μ?(el), of 2.47(11)D and 3.42(6)D for the [11.9]Ω = 3∕2 and X (2)Π(3∕2)states, respectively. The observed trend in μ?(el) for the PtX (X = C,N,O,S and F) series is discussed and a comparison with IrF made.     

Microwave spectrum,structure, quadrupole coupling constants and dipole moment of carbon monoxide-borane

The J = 0 → 1 and J = 1 → 2 transitions of thirteen isotopic species of carbon monoxide-borane (BH₃CO) have been measured. The heavy atom r₂ structural parameters have been calculated in several ways so as to minimize the effects of the small carbon coordinate. The structural parameters found are: d(B-C) = 1.534 ± 0.01 Å, d(C-O)= 1.135 ± 0.01 Å. d(B-H)= 1.221 ± 0.001 Å, ∠HBC = 103.79 ± 0.06°, and ∠HBH = 114.50 ± 0.15°. In addition, a complete r₀ structure has been calculated by least-squares fitting the moments of inertia of all the isotopic species. A dipole moment of 1.698 ± 0.02 D was determined.     

Improved mesophase stability of benzoxazole derivatives via dipole moment modification

By modifying the molecular dipole moments with lateral monofluorine substituent, improved mesophase stabilities were obtained for novel benzoxazole derivatives, 2-(4?-alkoxy-3-fluorobiphenyl-4-yl)-benzoxazole liquid crystals (coded as nPPF(3)Bx). The series of nPPF(3)Bx with lateral monofluorine substituent ortho to benzoxazole group have larger calculated dipole moments by about 2 D than the corresponding fluorine-substituted analogs (compounds I) with lateral monofluorine ortho to alkoxy group; it is interesting to note that they show lower melting and clearing points but better mesophase stability with wider mesophase ranges for the molecules with both polar (NO₂, Cl) and nonpolar (CH₃, H) terminal groups. Meanwhile, compounds nPPF(3)Bx show greater red-shifted photoluminescence emissions than compounds I, which suggest that π–π interaction between molecules is reinforced by the enhanced dipole–dipole interaction caused by increased dipole moments. These results suggest that modification of the molecular dipole moment is an effective method to improve the mesophase stability of the classical mesogenic compounds.     

The permanent electric dipole moment and hyperfine interaction in ruthenium monoflouride (RuF)

Ruthenium monofluoride, RuF, has been detected using low-resolution laser-induced fluorescence (LIF) in the visible and near infrared spectral regions. A visible band, designated as [18.2]5.5-X 4Phi(9/2), has been recorded field-free and in the presence of a static electric field using high-resolution LIF spectroscopy. The r0 internuclear distances for the [18.2]5.5 and X 4Phi(9/2) states were determined to be 1.911 and 1.916 A, respectively. The vibrational interval DeltaG(1/2) of 534(15) cm-1 for the X 4Phi(9/2) state was determined from the analysis of the dispersed LIF. The Stark shifts of the visible band were analyzed to produce permanent electric dipole moments of 1.97(8) and 5.34(7) D for the [18.2]5.5 and X 4Phi(9/2), states, respectively. The fluorine magnetic hyperfine structure associated with spectral features was analyzed. The hyperfine structure and dipole moments are interpreted using a molecular-orbital correlation model and compared with FeF and other ruthenium-containing molecules.     

Theoretical study of the dipole moment of oxygen monofluoride (OF)

Theoretical X²II potentials and dipole moment functions for OF are presented at the CASSCF, externally contracted Cl, and MRCI(SD) levels using DZP and extended gaussian basis sets. The best theoretical results (with experiment in parentheses) are μ_ν =0 = ?0.0089 (?0.0043) and μ_ν=1 = ?0.0318 (?0.0267) D, where the minus sign implies O⁺F^?.     

Microwave spectroscopic determination of the dipole moment of cyclopropenylidene,C3H2

Stark effects were measured for the 2₁₂-1₀₁ (85 GHz) and 4₄₁-3₃₀ (266 GHz) transitions of cyclopropenylidene, C₃H₂ with a parallel-plate cell designed for transient molecules. From the least-squares analysis of the Stark shifts the dipole moment of C₃H₂ was determined to be 3.43(2) D, where the error is three standard deviations. The dipole moment obtained is in good agreement with predictions by ab initio calculations.     

Spectroscopic investigation of magnetic dipole allowed transitions through the magnetic transition moment

An experimental technique for detecting magnetic dipole allowed transitions by their dispersion-induced circular dichroism (DICD) is discussed. The DICD spectra of three nitrogen heterocycles (pyridine, pyrazine and tetraphenylporphyrin) are shown to be dominated by the n — π^* transitions, as distinct from the normal absorption spectra which are dominated by the electric dipole allowed π — π^* bands.