Mise en evidence de la polarisation d'une onde de surface par absorption atomique

Particular polarisation of surface waves is demonstrated using hyperfine dipolar magnetic transitions. We compare the relative intensities of F = 2, M = 2 ? F = 1, M = 1 andF = 2, M =-2 ? F = 1, M = -1 lines in the fundamental state of ⁸⁷Rb     

Assignment of submillimeter laser lines in CH3I

We propose explanations for three laser lines observed in CH₃I by Dyubko, Svich and Fesenko. Two lines are respectively assigned to (J = 16, K = 6) → (J = 15, K = 6) and (J = 45, K = 6) → (J = 44, K = 6) in the ν₆ = 1 state. Th e third one might be explained as (ν₃ = 2, J = 54, K) → (ν₃ = 2, J = 53, K).     

The microwave spectra and structures of epihalohydrins: Epichlorohydrin

The microwave spectrum of the two chlorine isotopic species of epichlorohydrin ($\text{CH}{}_2\text{OCH}$CH₂Cl) is reported. The structure is a gauche conformation with the Cl atom twisted toward the oxygen side of the ring. The observed rotational constants (in MHz) and centrifugal distortion constants (in kHz) are: C₂H₃OCH₂³⁵Cl; A = 13 373.02, B = 2080.353, C = 1932.469, Δ_JK = ? 6, Δ_K = 2400, δ_J = ? 0.43, δ_K = 17, H_KJ = ? 0.13, H_K = 570, h_JK = 0.061, h_K = ? 5.1: C₂H₃OCH₂³⁷Cl; A = 13 361.24, B = 2028.853, C = 1887.990, Δ_JK = 0.31, Δ_K = 1669., δ_J = ? 0.16, δ_K = 54.1.     

Stark-hyperfine measurements in K = 0 and K = 1 states of NH3

High-resolution Stark-hyperfine transition measurements have been made on the J = 1, K = 0 and J = 1, K = 1 levels of ammonia using molecular beam electric resonance spectroscopy. The dipole moments measured are μ(J = 1, K = 0) = 1.47149(15) D and μ(J = 1, K = 1) = 1.47179(15) D. The polarizability anisotropy was found to be positive and hyperfine properties for both states were accurately measured.     

The microwave spectrum and conformations of halomethyl oxiranes: Bromomethyl oxirane

The microwave spectrum of bromomethyl oxirane

has been recorded in the range 12.5–18 and 26.5–40 GHz. Lines of the two bromine isotopic species of three rotamers, gauche-1 (Br near the O atom), gauche-2 (Br near the CH₂ of the ring) and cis have been identified. The gauche-1 lines are strongest, and the cis lines the weakest. The rotational constants (in MHz) are: gauche-1 (⁷⁹Br) A = 12 296.050, B = 1 391.677, C = 1 317.360, (⁸¹Br) A = 12 199.162, B = 1 378.321, C = 1 309.142; gauche-2 (⁷⁹Br) A = 12 278.436, B = 1 378.830, C = 1 304.852, (⁸¹Br) A = 12 189.869, B = 1 369.696, C = 1 301.584; cis (⁷⁹Br) A = 7 733.314, B = 1 808.087, C = 1 737.340, (⁸¹Br) A = 7 726.16, B = 1 801.159, C = 1 730.125.     

The microwave spectrum of vinyl azide

Vinyl azide has been shown to exist in both cis and trans conformations with the cis more stable by 460 cal/mole. The rotational constants in Megahertz are: cis, A = 14 698.23, B = 4088.44, C = 3195.64; trans, A = 46 761.19, B = 2751.40, C = 2598.83. The dipole moment components (in debye) are: cis, μ_a = 1.337, μ_b = 0.326, μ_total = 1.376; trans, μ_a = 1.156, μ_b = 0.900, μ_total = 1.465.     

The microwave spectra,conformations, and dipole moments of 4-cyanocyclopentene

Microwave spectra have been observed and assigned for the axial and equatorial conformations of 4-cyanocyclopentene. For the axial species the rotational constants in megahertz are A = 5095.77, B = 2185.81, and C = 1936.50; for the equatorial species the values are A = 6762.66, B = 1916.72, and C = 1590.60. Dipole moment measurements yielded |μ_a| = 3.48 D and |μ_c| = 2.51 D for the axial form and |μ_a| = 3.85 D and |μ_c| = 1.10 D for the equatorial form. Relative intensity measurements showed the equatorial conformer to be 400 ± 60 cal mole^?1 lower in energy. Several sets of vibrational satellites were observed and natural abundance C¹³ spectra were obtained for the equatorial conformer.     

Microwave spectrum,centrifugal distortion constants,and quadrupole coupling constants of 3-chloropyridine

The microwave spectrum of 3-chloropyridine has been measured in the frequency region of 8.2 to 18 GHz. The rotational constants, centrifugal distortion constants, and the quadrupole coupling constants for the ³⁵Cl species are A = 5839.448 ± 0.027 MHz, B = 1604.152 ± 0.005 MHz, C = 1258.327 ± 0.004 MHz, Δ_J = 0.10 ± 0.01 KHz, Δ_JK = 0.36 ± 0.09 KHz, Δ_K = 1.18 ± 0.07 KHz, δ_J = ?0.008 ± 0.005 KHz, δ_K = 0.88 ± 0.20 KHz, χ_aa = ?70.04 ± 0.38 MHz, χ_bb = 36.68 ± 0.19 MHz. The values of rotational constants and quadrupole coupling constants for the ³⁷Cl species are A = 5840.052 ± 0.034 MHz, B = 1559.354 ± 0.01 MHz, C = 1230.739 ± 0.016 MHz, χ_aa = ?54.20 ± 1.26 MHz, χ_bb = 29.49 ± 0.48 MHz. The double bond character in the CCl bond is found to be 2%. The smaller than expected value of rotational constant A points to a “fattening” of the pyridine ring about the a-axis in contrast to 2-chloropyridine, where no such substitution effect was observed.     

Critical behavior of the specific heat of dysprosium near the néel temperature

The heat capacity has been measured in Dy near its Néel temperature. Careful analysis of the data shows an apparent change in the sign of the exponent α at t_d ～ 0.005. The outer region behaves universally with ? = 1, n = 2 systems, having α = α′ = ? 0.02 ± 0.01, and the inner region has α = α′ = + 0.18 ± 0.08, in agreement with predictions for anisotropic dipolar-dominated systems.     

The microwave spectrum of urea

The microwave spectrum of urea has been recorded between 5 and 50 GHz. The rotational constants obtained from a least-squares fit of 47 b-type transitions are A = 11233.333, B = 10369.369, C = 5416.668 MHz. Centrifugal distortion constants were evaluated subject to the planarity constraints, giving satisfactory agreement up to at least J = 20. They are: τ_aaaa = ?0.04423, τ_bbbb = ?0.04075, τ_aabb = 0.02268, τ_abab = ?0.02806. The diagonal elements of the nuclear quadrupole coupling tensor are χ_aa = 2.16, χ_bb = 1.88, χ_cc = ?4.04. The dipole moment is μ = μ_b = 3.83 D (12.8 × 10^?30 Cm).     

Microwave spectrum of fluoroacetyl chloride

The microwave spectrum of fluoroacetyl chloride has been studied in the 8–40 GHz region and transitions arising from one conformer have been assigned. This conformer has all the heavy atoms in a plane with the fluorine and chlorine atoms trans to one another. The rotational constants and nuclear quadrupole coupling constants for the ground vibrational state are (in MHz): H₂FCCO³⁵Cl: A = 9025.82, B = 2403.92, C = 1920.70, χ_aa = ?47.7, χ_bb = 23,7, χ_cc = 24.1; H₂FCCO³⁷Cl: A = 8994.95, B = 2342.24, C = 1879.75, χ_aa = ?38.0, χ_bb = 18.9, χ_cc = 19.1. The spectrum of the first excited torsional state has been assigned. Some lines possibly due to a second conformer have been observed but not yet assigned.     

The microwave spectrum,structure and nuclear quadrupole coupling constants for stibabenzene

The microwave spectrum of 121-SbC₅H₅, 123-SbC₅H₅, β-dideutero 121-SbC₅H₃D₂ and 123-SbC₅H₃D₂ has been assigned in the region 26.5–40.0 GHz. The respective rotational constants and uncertainties are: A = 4512.69 ± 0.42, B = 1738.00 ± 0.01, C = 1254.51 ± 0.01; A = 4512.84 ± 0.30, B = 1729.80 ± 0.01, C = 1250.22 ± 0.01; A = 4176.18 ± 0.33, B = 1660.94 ± 0.01, C = 1188.15 ± 0.01; A = 4176.60 ± 0.61, B = 1652.94 ± 0.03, C = 1184.03 ± 0.03 (in MHz units). The structure is found to be planar, C_2v in symmetry. The $\text{d(}\text{Sb-C}\text{) = 2.050 ± 0.005}\text{A}\text{?}$ and ∠CSbC = 92.9° ± 1.0°. The nuclear quadrupole coupling constants for the 121 and 123 antimony isotopes are χ_aa = 456.4 ± 4.1 MHz, η = 0.396 ± 0.008, and χ_aa = 583.00 ± 5.3 MHz, η = 0.399 ± 0.008, respectively. Several alternate techniques using the coupling constants as data support a σ-donating property for antimony.     

Angular correlation study of levels in 16C

Angular correlation measurements using the ¹⁴C(t, pγ)¹⁶C reaction result in the following spin assignments to levels in ¹⁶C: E_x = 1.766 MeV, J = 2; E_x = 3.980 MeV, J = 2; E_x = 4.083 MeV, J = 3; E_x = 4.138 MeV, J = 4.     

Microwave spectrum,conformation, and quadrupole coupling constants of 1-iodopropane

The molecular rotational spectrum of 1-iodopropane (n-propyl iodide) has been investigated in the frequency region 9–33 GHz. The 1-iodopropane molecule has been confirmed to exist in two rotational isomers, trans and gauche. The rotational constants of the ground state were determined to be A = 10 595.450(60) MHz, B = 1781.669(8) MHz, and C = 1614.200(7) MHz for gauche, and B = 1305.247(8) MHz and C = 1269.365(7) MHz for trans. The nuclear quadrupole coupling constants were determined to be χ_aa = −1020(3) MHz, χ_bb = 193(2) MHz, χ_cc = 827(4) MHz, χ_ab = 1173(2) MHz, χ_ac = −369(7) MHz, and χ_bc = 230(5) MHz for gauche, and χ_aa = −1509(8) MHz, χ_bb = 610(9) MHz, χ_cc = 899(12) MHz, and χ_ab = −789(9) MHz for trans. The centrifugal distortion constants were also determined using all of the assigned transitions. From the relative intensity measurements the skeletal torsional frequencies for the gauche and trans forms were estimated to be 117 and 108 cm⁻¹, respectively.     

ESR studies of Cu2+ doped in SrC4H4O6·3H2O single crystals

Electron spin resonance spectra of Cu²⁺ doped in single crystals of strontium tartrate trihydrate grown by a diffusion technique have been investigated at 77K. Copper enters the lattice substitutionally and is trapped at two magnetically inequivalent sites. ESR measurements gave the following values for the spin-Hamiltonian parameters. Cu²⁺(I): g_gg = 2.0380, g_yy = 2.1317, g_zz = 2.3918 and A_xx = 26.3 G, A_yy = 56.3 G, A_zz = 110.8 G. Cu²⁺(II): g_xx = 2.0497, g_yy = 2.1297, g_zz = 2.3706 and A_xx = 19.2 G, A_yy = 61.4 G, A_zz = 107.2 G.     

Exactly solvable spin-12 quantum chains with multispin interactions

A generalized spin-$\text{1}\text{2}$ quantum chain with m (n) spin interactions for the z (x) component of the spins is shown to be self-dual. Through duality, the m arbitrary, n = 2 version of the model is transformed into m independent Ising chains in a transverse field, allowing us to get the exact values of the critical exponents for any m (v = s = z = 1; β = m/8; n_x = m/4) and the spectrum. The anisotropic XY chain is a particular case with = 2.     

Microwave spectrum of gauche normal propyl bromide

The microwave spectra of the two ⁷⁹Br and ⁸¹Br isotopic species of normal propyl bromide were measured in the frequency region 10–30 GHz. The a-type R-branch and b-type Q-branch transitions of one conformer, gauche, were assigned and the rotational constants of the ground state were determined to be A = 11 034.346, B = 2277.725, and C = 2024.525 MHz for the ⁷⁹Br species, and A = 11 027.924, B = 2261.019, and C = 2011.115 MHz for the ⁸¹Br species. The nuclear quadrupole coupling constants were determined to be χ_aa = 256.9, χ_bb = ?9.5, χ_cc = ?247.4, and |χ_ab| = 380.0 MHz for ⁷⁹Br species and χ_aa = 214.1, χ_bb = ?8.1, χ_cc = ?206.0, and |χ_ab| = 311.9 MHz for ⁸¹Br species. Assuming the values of χ_bc and χ_ca to be zero, the principal values of the χ tensor have been evaluated to be χ_xx = ?279.0, χ_yy = ?247.4, χ_zz = 526.4 MHz for ⁷⁹Br species and χ_xx = ?228.1, χ_yy = ?206.0, and χ_zz = 434.1 MHz for ⁸¹Br species. From the relative intensity measurements the energy differences between the ground and first excited states, and the ground and second excited states, associated with the central CC torsion around the α and β carbon bonds were found to be 127 and 211 cm^?1, respectively.     

Microwave spectrum,structure, quadrupole coupling constants,dipole moment,and barrier to internal rotation of N-methylhydroxylamine

The microwave spectrum has been observed and analyzed for five isotopic species of N-methylhydroxylamine. For the normal species the rotational constants (in Megahertz) are A = 38 930.771 ± 0.005, B = 3939.607 ± 0.002, and C = 8690.716 ± 0.001. These data show that the molecule exists in the trans conformation, with structural parameters that include the following: CN = 1.460, NO = 1.461, NH = 1.007, and OH = 0.962. Hyperfine structure analyses have yielded the complete inertial axis ¹⁴N quadrupole coupling constant tensor, and thus the tensor values in the electric field-gradient principal axis system as follows: χ_xx = 4.41 ± 0.30, χ_yy = 1.93 ± 0.45, and χ_zz = ?6.34 ± 0.30 MHz. The total electric dipole moment has been found to have the value μ_T = 0.71 D, and the barrier to internal rotation of the methyl group is 3.55 kcal/mole.     

Microwave spectrum of 3-lodopropene in its torsionally excited states

The microwave spectra of the skew-3-iodopropene in its torsionally excited state were studied in the region 15 to 23 GHz. From the analyses of the a-type R-branch and b-type Q-branch transitions, the rotational constants and the elements of the χ-tensor were obtained: A₁ = 17 783.84 ± 0.77, B₁ = 1591.26 ± 0.02, C₁ = 1540.24 ± 0.02, χ_aa = ?1333 ± 8, χ_bb = 386 ± 4, χ_cc = 947 ± 6, and |χ_ab| = 1086 ± 2, each in MHz for the first torsionally excited state, and A₂ = 17 915.85 ± 1.38, B₂ = 1594.49 ± 0.03, C₂ = 1541.85 ± 0.03, χ_aa = ?1319 ± 10, χ_bb = 383 ± 5, χ_cc = 936 ± 8, and |χ_ab| = 1073 ± 3, each in MHz for the second torsionally excited state, respectively. From the observed line intensity, the torsional frequencies of the CH₂I group between the ground and the first excited states and also between the first and second excited states were obtained to be 114 ± 34 and 80 ± 24 cm^?1, respectively.     

Microwave spectrum,molecular structure,and nuclear quadrupole coupling constants of 3-bromopropene

The microwave spectra of the two ⁷⁹Br and ⁸¹Br isotopic species of 3-bromopropene were measured in the frequency region 14–23 GHz. The R and Q branches for a- and b-type rotational transitions of one conformer, skew, have been assigned and the rotational constants of the ground state have been determined to be A = 19 247.56 MHz, B = 1975.339 MHz, and C = 1914.761 MHz for ⁷⁹Br species, and A = 19 234.26 MHz, B = 1961.417 MHz, and C = 1901.563 MHz for ⁸¹Br species, respectively. By the analysis of the second-order perturbation treatment of the quadrupole interaction, it is found that the χ_ab element of the χ tensor primarily contributes to the anomalous hyperfine splittings. The matrix elements of products of direction cosines in terms of the symmetric top wavefunctions have been derived. The nuclear quadrupole coupling constants have been determined χ_aa = 384.2 MHz, χ_bb = ?71.9 MHz, χ_cc = ?276.3 MHz, and |χ_ab| = 358.7 MHz for ⁷⁹Br species and χ_aa = 283.2 MHz, χ_bb = ?55.6 MHz, χ_cc = ?227.6 MHz, and |χ_ab| = 296.0 MHz for ⁸¹Br species.