Analysis of torsional splittings in the microwave spectra of dimethylether,CH3OCH3 and its isotopes,CD3OCH3 and CD3OCD3

The multiplet splitting patterns of microwave transitions in the ground state and the first two torsional excited states of CH₃OCH₃, CD₃OCD₃, and CD₃OCH₃ were analyzed in terms of the semirigid rotor models C_2vF-C_3vT-C_3vT and $\text{C}{}_3\text{F-}\text{C}{}_{\mathrm{3v}}\text{T-}\text{C}{}_{\mathrm{3v}}\text{T}\text{?}$. The following nonzero potential coefficients were obtained for CH₃OCH₃: V₃₀ = V₀₃ = 909.05 ± 0.49 cm^?1, V′₃₃ = 5.06 ± 1.60 cm^?1; for CD₃OCH₃: V₃₀(CD₃) = 897.18 ± 2.41 cm^?1, V₀₃(CH₃) = 910.45 ± 0.33 cm^?1; for CD₃OCD₃: V₃₀ = V₀₃ = 897.00 cm^?1. These results are compared to earlier microwave studies of these molecules.     

Thioformaldehyde: Rotational analyses of the Ã1A2-X̃1A1 visible absorption system

The $\text{A}\text{?}{}^1\text{A}{}_2\text{-}\text{X}\text{?}{}^1\text{A}{}_1$ electronic absorption spectra of CH₂S and CD₂S have been photographed under high resolution. Selected bands have been rotationally analyzed by least squares line fitting and by band contour methods. Improved rotational constants have been obtained for the ground states of CH₂S and CD₂S by use of combination differences. Bands of all three polarizations appear in the electronic spectrum. The type A origin band is magnetic dipole allowed, whereas the 4₀¹ band is type B. Perturbations are identified in the 0₀⁰ and 3₀¹4₀³ bands of CH₂S. The rotational constant A in the upper state decreases rapidly, in accordance with theoretical calculations, as successive quanta of the inversion mode ν′₄ are excited. The planar inertial defect has a small positive value in the zero level of the upper state although the molecule is slightly nonplanar; the r₈ geometry is $\text{r(}\text{CH}\text{) = 1.082}\text{A}\text{?}$, $\text{r(}\text{CS}\text{) = 1.701}\text{A}\text{?}$, angle HCH = 120°, and the out-of-plane angle is approximately 10°.     

Microwave spectrum of fluorodihydroxy borane,BF(OH)2

Fluorohydroxy borane, BF(OH)₂, has been identified in the hydrolysis of trifluoroborane by microwave spectroscopy. The rotational and centrifugal distortion constants have been determined for the normal and d₂ species. From these constants the molecular structure has been determined. This molecule does not have C₂ symmetry and the structural parameters are $\text{r}\text{(BO}{}_1\text{) = 1.360}\text{A}\text{?}$, $\text{r}\text{(BO}{}_2\text{) = 1.365}\text{A}\text{?}$, ∠FBO₁ = 118.2°, and ∠FBO₂ = 121.0°. The inertia defects establish the planarity of the molecule. The dipole moment of 1.818 ± 0.007 D has been obtained from the measurements of the Stark effects.     

Susceptibilities of the S = 12 XY model on the square lattice at T = 0

For the $\text{S =}\text{1}\text{2}\text{XY}$ model at T = 0 four susceptibilities have been calculated exactly on a sequence of finite square lattices and extrapolated to the infinite square lattice. For the ferromagnet χ_zz = 0 while χ_xx ～ N^2.9; for the antiferromagnet $\text{J}{}_{\mathrm{\chi xx}}\text{N(gμ}{}_{\mathrm{<mtext>B</mtext>}}\text{)}{}^2\text{= 0.025 ± 0.002}$ and $\text{J}{}_{\mathrm{\chi xx}}\text{N(gμ}{}_{\mathrm{<mtext>B</mtext>}}\text{)}{}^2\text{= 0.13 ± 0.03}$.     

The microwave spectrum,substitution structure,and dipole moment of thioketen,H2CCS

The microwave spectrum of the unstable thiocarbonyl thioketen, H₂CCS, has been investigated in the region 26.5–40 GHz. All singly substituted species as well as D₂CCS have been studied and the derived rotational constants yield the following structural parameters: $\text{r}{}_{\mathrm{<mtext>s</mtext>}}\text{(CS) = 1.554 ± 0.003}\text{A}\text{?}$, $\text{r}{}_{\mathrm{<mtext>s</mtext>}}\text{(CC) = 1.314 ± 0.003}\text{A}\text{?}$, $\text{r}{}_{\mathrm{<mtext>s</mtext>}}\text{(CH) = 1.090 ± 0.006}\text{A}\text{?}$, ∠_s(HCH) = 120.3 ± 0.5°. The dipole moment is μ = 1.02 ± 0.01 D. Four low frequency vibrational modes have been observed and their assignments are discussed.     

The microwave spectrum of 1-phosphapropyne,CH3CP: Molecular structure,dipole moment,and vibration-rotation analysis

The J = 4 ← 3 and J = 3 ← 2 rotational transitions of 1-phosphapropyne, CH₃CP, between 26.5 and 40 GHz have been studied by microwave spectroscopy. The spectrum shows the characteristic vibration-rotation satellite patterns associated with a C_3v symmetric rotor. Apart from the most abundant isotope variant, the species ¹²CD₃¹²C³¹P, ¹²CD₂H¹²C³¹P, ¹²CH₂D¹²C³¹P, ¹³CH₃¹²C³¹P, ¹²CH₃¹³C³¹P, ¹³CD₃¹²C³¹P, and ¹²CD₃¹³C³¹P have also been studied. For ¹²CH₃¹²C³¹P the rotational constants B₀ = 4991.339 ± 0.003 MHz, D_J = 0.823 ± 0.092 kHz, D_JK = 66.59 ± 0.18 kHz have been determined. From these data the following structural parameters have been derived: $\text{r}{}_{\mathrm{s}}\text{(}\text{CH}\text{) = 1.107 ± 0.001}\text{A}\text{?}$, ∠_s(HCC) = 110.30 ± 0.09°, $\text{r}{}_{\mathrm{s}}\text{(}\text{CC}\text{) = 1.465 ± 0.003}\text{A}\text{?}$, $\text{r}{}_0\text{(}\text{CP}\text{) = 1.544 ± 0.004}\text{A}\text{?}$. The dipole moment has been determined as 1.499 ± 0.001 D by analysis of the Stark effect of the J = 3 ← 2, |K| = 1 line. The vibrational satellites (v_s = 1, 2, and 3) have been studied and various vibration-rotation parameters derived.     

Microwave spectra of deuterated ethylenes: Dipole moment and rz structure

The pure rotational spectra of three deuterated ethylenes, CH₂CD₂, CH₂CHD, and cis-CHDCHD, were observed by microwave spectroscopy, and the rotational and centrifugal distortion constants were determined precisely. The dipole moment of CH₂CD₂ was calculated from the Stark effects to be 0.0091 ± 0.0004 D. From the observed rotational constants the average structure was calculated to be $\text{r}{}_{\mathrm{z}}\text{(CC)}\text{= 1.3391 ± 0.0013}\text{A}\text{?}$, $\text{r}{}_{\mathrm{z}}\text{(CH)}\text{= 1.0869 ± 0.0013}\text{A}\text{?}$, θ_z(CCH) = 121.28 ± 0.10°, and $\text{r}{}_{\mathrm{z}}\text{(CH)}\text{- r}{}_{\mathrm{z}}\text{(CD)}\text{= 0.00137 ± 0.00037}\text{A}\text{?}$, where the errors include one standard deviation in the fitting and errors due to an uncertainty (±0.03°) in θ_z(CCH) - θ_z(CCD).     

The quadrupole moments of the 5− states in 116Sn, 118Sn and 120Sn

The quadrupole interaction frequencies $\text{ω}{}_0\text{=}\text{3eQ}{}_1\text{V}{}_{\mathrm{zz}}\text{41(21-1)}\text{h}\text{?}$ in the 5^? state of ¹¹⁸Sn have been measured by time differential perturbed angular correlation technique in Sn, Sb and (95% Sn+5% Sb) environments. The ω₀ for ¹¹⁶Sn was determined in Sn environment only. With the help of the known electric field gradient ¹) of Sn in a Sn lattice the quadrupole moments have been deduced as $\text{Q(5}{}^{\mathrm{?}}\text{,}{}^{118}\text{Sn}\text{) = ±0.10(4) b}\text{and}\text{Q(5}{}^{\mathrm{?}}\text{,}{}^{116}\text{Sn}\text{) = ±0.165(60)}\text{b}$. These values together with the known²) quadrupole moment of the analogous 5^? state in ¹²⁰Sn are interpreted in terms of the pure single-particle model. The data exhibit the expected strong systematic variation of Q_I with the number of particles in the h_{$\text{11}\text{2}$}. subshell which is being filled with 1, 3 and 5 neutrons in ¹¹⁶Sn, ¹¹⁸Sn, and ¹²⁰Sn, respectively.     

Strengths and lorentz broadening coefficients for spectral lines in the ν3 and ν2 + ν4 bands of 12CH4 and 13CH4

Line strengths and self- and nitrogen-broadened half-widths were measured for spectral lines in the ν₃ and ν₂ + ν₄ bands of ¹²CH₄ and ¹³CH₄ from 2870–2883 cm^?1 using a tunable diode laser spectrometer. From measurements made over a temperature range from 215 to 297 K, on samples of ¹²CH₄ broadened with N₂, we deduced that the average temperature coefficients n, defined as $\text{b}{}_{\mathrm{<mtext>L</mtext>}}{}^0\text{(T) = b}{}_{\mathrm{<mtext>L</mtext>}}{}^0\text{(T}{}_0\text{)(}\text{T}\text{T}{}_0\text{)}{}^{\mathrm{?n}}$, of the Lorentz broadening coefficients for the ν₃ and ν₂ + ν₄ bands of ¹²CH₄ were 0.97 ± 0.03 and 0.89 ± 0.04, respectively. A smaller increase is observed in line half-width with increasing pressure for E-species lines, for both self- and nitrogen-broadening, than for other symmetry species lines over the range of pressures measured, 70 to 100 Torr.     

Infrared spectroscopic studies of partially deuterated ethanes and the r0, rz, and re structures

Samples of CH₃CH₂D, CH₃CHD₂, CD₃CH₂D, and CD₃CHD₂ have been prepared, and their infrared spectra recorded. Analysis of type B or type C “perpendicular” bands has enabled the rotational parameter ($\text{A}{}_0\text{-}\text{B}{}_0$) to be determined for all four species. These have been combined with existing infrared, Raman, and microwave data for CH₃CH₃, CD₃CD₃, and CH₃CD₃ species, to determine the ground state (r₀) and ground state average (r_z) structures within narrow limits. Zero point energy effects on the average structure are determined to be a CH bond shortening of 0.0015(3) Å and an HCC angle opening of 0.010(5)° on deuteration. These effects enable the equilibrium structure of ethane to be estimated. The r_z(CC) bond length is determined to be 1.5351(2) Å, which is significantly longer than previous estimates involving electron diffraction data.     

The microwave spectrum,structure, and dipole moment of the unstable molecule phosphaethene,CH2PH

A detailed rotational analysis of the microwave spectrum between 26.5 and 40 GHz of phosphaethene, CH₂PH, has been carried out. This molecule is the simplest member of a new class of unstable molecules—the phosphaalkenes. The species can be produced by pyrolysis of (CH₃)₂PH, CH₃PH₂ and also somewhat more efficiently from Si(CH₃)₃CH₂PH₂. Full first-order centrifugal distortion analyses have been carried out for both ¹²CH₂³¹PH and ¹²CH₂³¹PD yielding: A₀ = 138 503.20(21), B₀ = 16 418.105(26), and C₀ = 14 649.084(28) MHz for ¹²CH₂³¹PH. The 1₀₁-0₀₀μ_A lines have also been detected for ¹³CH₂PH, cis-CDHPH and trans-CHDPH. These data have enabled an accurate structure determination to be carried out which indicates: $\text{r(}\text{H}{}_{\mathrm{c}}\text{C}\text{) = 1.09 ± 0.015}\text{A}\text{?}\text{, ∠(}\text{H}{}_{\mathrm{c}}\text{CP}\text{) = 124.4 ± 0.8°; r(}\text{H}{}_{\mathrm{t}}\text{C}\text{) = 1.09 ± 0.015}\text{A}\text{?}\text{, ∠(}\text{H}{}_{\mathrm{t}}\text{CP}\text{) = 118.4 ± 1.2°; r(}\text{CP}\text{) = 1.673 ± 0.002}\text{A}\text{?}\text{, ∠(}\text{HCH}\text{) = 117.2 ± 1.2°; r(}\text{PH}\text{) = 1.420 ± 0.006}\text{A}\text{?}\text{, ∠(}\text{CPH}\text{) = 97.4 ± 0.4°}$. The dipole moment components have been determined as μ_A = 0.731 (2), μ_B = 0.470 (3), μ = 0.869 (3) D for CH₂PH; μ_A = 0.710 (2), μ_B = 0.509 (10), μ = 0.874 (7) D for CH₂PD.     

Microwave measurements and calculations of quadrupole coupling effects in CH3I and CD3I

The transitions J = 1 ← 0, K = 0; J = 2 ← 1, K = 0; and J = 2 ← 1, K = 1 of CH₃I and CD₃I were measured using a Stark-modulated microwave spectrometer. Iodine quadrupole coupling strengths were analyzed to determine variations with deuterium substitution on the methyl group and variations with centrifugal distortion. Quadrupole coupling strengths were described by the expression $\text{eQq}{}_0\text{+ aJ(J + 1) + bK}{}^2\text{+}\text{cK}{}^4\text{J(J + 1)}$. Explicit expressions are given for a, b, and c for a symmetric top in terms of molecular parameters. For CH₃I eQq₀ = ?1934.11 ± 0.02 MHz and for CD₃I eQq₀ = ?1928.95 ± 0.04 MHz. Rotational constants obtained are B(CH₃I) = 7501.274 ± 0.002 MHz and B(CD₃I) = 6040.298 ± 0.007 MHz. The observed fractional change in halogen quadrupole coupling of 0.0027 is related to previous results for methyl chloride and methyl bromide.     

A theoretical model for the interacting upper states of the ν1, ν3, 2ν2, ν2 + ν4, and 2ν4 bands in methane

The effective vibration-rotation Hamiltonians complete to fourth order in the Amat-Nielsen scheme for the upper states of the ν₁, ν₃, 2ν₂, ν₂ + ν₄, and 2ν₄ bands in methane are reviewed, and the major vibration-rotation interactions (H₃₀, $\text{H}\text{?}{}_{40}$, $\text{H}\text{?}{}_{21}$, $\text{H}{}_{31}$, $\text{H}\text{?}{}_{22}$) connecting the different vibrational states are discussed. Explicit matrix elements in a basis of harmonic oscillator-symmetric rotor basis functions are given for the purely vibrational terms and for the vibration-rotation interactions. Expressions for spectral intensities of infrared and Raman spectra are presented, and the selection rules and transition moment matrix elements are stated. A computer program is described which, incorporating all these features, can be used for prediction of infrared and Raman spectra and for determination of molecular constants from observed spectra by a least-squares routine. As an example the program is applied to the 2ν₄ isotropic Raman spectrum of ¹²CH₄, leading to a very good agreement between the experimental and calculated spectra.     

Structure magnetique en champ applique nul de l'acetate de manganese tetrahydrate Mn(CH3COO)2, 4H2O

The magnetic structure of manganous acetate Mn(CH₃COO)₂, 4H₂O has been solved by neutron diffraction. Manganous acetate crystallizes in the space group $\text{P2}{}_1\text{c}$ with Z = 6. Manganese atoms (in position 2a and 4e) are located in (100) planes. Below T_N = 3.18 K this compound is antiferromagnetic in a zero applied field with the k vector [$\text{1}\text{2}$ 00]. The plane (100) is ferromagnetic. The magnetic group is $\text{P}{}_{\mathrm{2a}}\text{2}{}_1\text{c}$.     

Analysis of the (ν1 + ν2) and (ν2 + ν3) combination bands of ozone

The fine structures of the (ν₁ + ν₂) and (ν₂ + ν₃) combination bands of ozone in the 5.7-μm region have been recorded and analyzed. The two vibrational states are coupled through Coriolis and second-order distortion terms. The interaction has been treated by the numerical diagonalization of the secular determinant for the two coupled states. With the centrifugal distortion parameters fixed to the ground state values, the following constants have been obtained: ν₁ + ν₂ = 1796.26₆, A₁₁₀ = 3.610₄, B₁₁₀ = 0.4414₅, $\text{C}{}^1{}_{110}\text{= 0.3902}{}_9$, ν₂ + ν₃ = 1726.52₆, A₀₁₁ = 3.553₇, B₀₁₁ = 0.4398₂, $\text{C}{}^1{}_{011}\text{= 0.3884}{}_4$, Y₁₃ = ?0.46₆, and X₁₃ = ?0.01₀ cm^?1. In addition, the following anharmonic constants have been obtained: x₁₂ = ?7.82₁ and x₂₃ = ?16.49₄ cm^?1. The value of the dipole moment ratio, $\text{R =}\text{〈011|μ}{}_{\mathrm{z}}\text{|0〉}\text{〈110|μ}{}_{\mathrm{x}}\text{|0〉}$, is 1.30 ± 0.10.     

Diode laser measurements of intensities,N2-broadening,and self-broadening coefficients of lines of the ν2 band of 14N16O2

A diode laser spectrometer (resolution 0.0013 cm^?1) was used to record, in the 12-μm region, high-quality spectra of the ν₂ band of NO₂. Using these spectra, it was possible to obtain the N₂-broadening coefficients and an average self-broadening coefficient from measurements made for seven lines of this band. In addition, 30 single spin-component line intensities were measured. From them, through a least-squares fit, the purely vibrational transition moment of the ν₂ band, as well as two correcting rotational terms involved in the expansion of the transition moment operator, were obtained. These results led to the determination of the dipole moment derivative $\text{?μ}{}_{\mathrm{x}}\text{?q}{}_2\text{= ?0.0604}{}_1\text{± 0.0037}\text{D}$. It was also demonstrated that there is good consistency between the correcting terms deduced from the observed intensities and their theoretical estimates. Finally, a complete spectrum of the ν₂ band of NO₂ was computed, providing a total band intensity S_v(ν₂) = 0.542 × 10^?18cm^?1/molecule cm^?2 at 296 K.     

Laser magnetic resonance spectrum of BrO (2Π12 ← 2Π32)

Magnetic dipole transitions between the ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and ${}^2\text{Π}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ components of the ground electronic state of BrO have been detected using the technique of laser magnetic resonance on three CO₂ laser lines between 964 and 970 cm^?1. This is the first direct observation of the ${}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ state in BrO. The spin-orbit splitting parameter, A, is determined to be ?967.9831(2) cm^?1 for ⁷⁹Br¹⁶O and ?967.9981(2) cm^?1 for ⁸¹Br¹⁶O. Accurate values for the rotational constant $\text{B}{}^{\mathrm{<mtext>eff</mtext>}}\text{(}{}^2\text{Π}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}$, the hyperfine parameters ($\text{b}{}_{\mathrm{F}}\text{+}\text{2c}\text{3}$) and d, the Λ-doubling parameter p, and the Zeeman parameter g| are also determined from an analysis of the measured spectra.     

The EPR and LMR spectra of the DO2 radical: Determination of ground-state parameters

The detection of lines in both the gas phase EPR spectrum at 9 GHz and the far-infrared LMR spectrum of the DO₂ radical is reported. The measurements are fitted with an appropriate Hamiltonian and several parameters for the molecule in the $\text{X}\text{?}{}^2\text{A″}$ state are determined. The majority of the transitions in the EPR spectrum are K-type doubling transitions and involve the a-component of the electric dipole moment. However the observation of one b-type transition (5₀₅-4₁₄) permits the determination of the off-diagonal component of the spin-rotation tensor, ?_ab, and an estimate of the relative magnitudes of the a- and b-components of the dipole moment. A combination of the parameters for HO₂ with those for DO₂ leads to a better understanding of the properties of the molecule. In particular, the r₀ molecular geometry has been determined more reliably than previously to be $\text{r}{}_0\text{(OH) = 0.9774}\text{A}\text{?}$, $\text{r}{}_0\text{(OO) = 1.3339}\text{A}\text{?}$, ∠HOO = 104.15°.     

nπ1 Transitions in tetramethyl-1,3-cyclobutanedithione-h12 and -d12

The polarized low-temperature crystal absorption spectra of tetramethyl-1,3-cyclobutanedithione-h₁₂ and -d₁₂ have been measured in the visible region, and $\text{nπ}{}^1$ excited states identified as follows: ³A_u with origin ($\text{h}{}_{12}\text{d}{}_{12}$) at $\text{16 829}\text{16 836}\text{cm}{}^{\mathrm{?1}}$; ¹A_u and ¹B₁₀ with nearly degenerate origins near 18 000 cm^?1; and probably ¹A_u and ¹B_1g near 19 500 cm^?1. The singlet excited states lie close together and perturb each other strongly. As in the corresponding dione, $\text{CH}\text{CD}$ stretching vibrations of the substituent methyl groups are active in intensity borrowing, and the effects of excitation are delocalized over the entire molecule.     

The ã3A2 ← X̃1A1 absorption spectrum of thioformaldehyde: A vibrational and rotational analysis

The results of a vibrational and rotational analysis of the banded $\text{a}\text{?}{}^3\text{A}{}_2\text{←}\text{X}\text{?}{}^1\text{A}{}_1$ transition in $\text{CH}{}_2\text{S}\text{CD}{}_2\text{S}$ are presented. Only three of the six vibrational modes are active in the spectrum with $\text{ν′}{}_2\text{=}\text{1320}\text{1012}$, $\text{ν′}{}_3\text{=}\text{859}\text{798}$, and $\text{2ν′}{}_4\text{=}\text{711}\text{516}\text{cm}{}^{\mathrm{?1}}$. The spin forbidden transition gains intensity primarily by a mixing of the ${}^1\text{A}{}_1\text{(π}{}^1\text{,π)}$ and ${}^3\text{A}{}_2\text{(π}{}^1\text{,n)}$ states. This is confirmed by a rotational analysis of the 0₀⁰ band of both isotopes. The rotational analysis shows that the coupling in the $\text{a}\text{?}{}^3\text{A}{}_2$ state is near Hund's case b and that the spin constants are nearly 10 times greater than those observed for CH₂O. A $\text{CNDO}\text{2}$ calculation shows that this difference is due to the greater spin orbit coupling of S in CH₂S and to the smaller energy differences between the $\text{B}\text{?}{}^1\text{A}{}_1\text{(π}{}^1\text{,π)}$, $\text{b}\text{?}{}^3\text{A}{}_1\text{(π}{}^1\text{,π)}$, $\text{X}\text{?}{}^1\text{A}{}_1$, and the $\text{a}\text{?}{}^3\text{A}{}_2\text{(π}{}^1\text{,n)}$ states. The r₀ structure calculated from the rotational constants is $\text{r}{}_{\mathrm{<mtext>CS</mtext>}}\text{= 1.683}\text{A}\text{?}$, $\text{r}{}_{\mathrm{<mtext>CH</mtext>}}\text{= 1.082}\text{A}\text{?}$, β_HCH = 119.6°, and α (out of plane) = 16.0°. A simultaneous fit of the vibrational levels in ν′₄ of CH₂S and CD₂S to a double minimum potential function yielded a barrier to molecular inversion of 13 cm^?1 and an equilibrium out-of-plane angle of 15°.