Rotational laser magnetic resonance spectroscopy of PH2(X 2B1)

Laser magnetic resonance spectra arising from eight rotational transitions of PH₂ in its vibronic ground state have been measured in the far infrared region. Analysis of the spectra yields more accurate rotational, centrifugal distortion and fine structure parameters than previous spectroscopic results. Determination of the isotropic an anisotropic hyperfine constant from the resolved ³¹P and proton hyperfine structure shows that the unpaired electron is essentially located in a 3p atomic orbital on the phosphorus atom.     

Analysis of hyperfine interactions of Fe IN FeF2, MnF2 and ZnF2

Analysis of magnetic hyperfine interactions of Fe²⁺ in FeF₂, Fe²⁺:MnF₂ and Fe²⁺:ZnF₂ yields a core polarization hyperfine field H_c = −514 ± 30 kOe and a value of 〈r⁻³〉_eff = 3.9 ± 0.04 au.     

The υ3 = 1 state of 37ClO2 studied by laser-microwave double resonance

Laser-microwave double-resonance experiments have been carried out which enable rotational and coupling constants of the υ₃ = 1 state of ³⁷ClO₂ to be determined. This work utilized an accidental coincidence between the 9R(24)C¹⁸O₂ laser line and hyperfine components of the ^QR_o(1) transition of the v₃ band of ³⁷ClO₂. A novel type of IR-MW-MW triple resonance is described.     

EPR study of the NO2+3 radical in irradiated K(UO2)(NO3)3 and K2(UO2)(NO3)4 single crystals

A new radical observed at low temperature in γ-irradiated K₂(UO₂)(NO₃)₄ single crystals has been tentatively assigned to a hitherto unknown oxyanion radical, NO²⁺₃. The assignment and the lack of ¹⁴N hyperfine structure, together with the g factors which are lower than the free-spin value, are discussed in terms of an orbital level scheme.     

Avoided-crossing molecular-beam spectroscopy of CH3SiF3

The avoided-crossing molecular-beam method has been applied to CH₃SiF₃ in the ground torsional state. Stark and hyperfine rotational anticrossings have been studied, along with barrier anticrossings in which the zero-field energy differences depend only on the torsionial splittings. For υ = 0, pure rotational spectra were measured forJ = 13 ← 12 and 14 ← 13 with a mm-wave spectrometer and for J = 1 ← 0 with the molecular-beam spectrometer. Stark and Zeeman studies have been carried out with conventional beam techniques. From a simultaneous analysis of existing microwave data for υ ? 2 and the current measurements, it was found that the moment of inertia of the methyl top I_α = 3.170(2) amu A², the effective rotational constants A^eff = 4059.522(22) Mhz, and the effective height of the barrier V₃^eff = 413.979(14) cm^?1. The true values of A and V₃ have been obtained within certain approximations. The rotational constant B and several distortion constants including D_K were evaluated. In addition to determining the electric dipole moment μ 2.33938(14) D, the data yielded values for the distortion dipole constants μ_D and μ_J, and the molecular g-factors g_| and g_⊥.     

Microwave—optical double resonance in the B 3Π0+ excited state of ICl

Pure rotational transitions were observed in the electronically excited state B ³Π₀⁺ of ICl. This state was populated by optical pumping with a single-mode dye laser. From the observed spectrum precise values of the quadrupole hyperfine coupling constant cqQ of iodine and the effective rotational constant were derived for both isotopes I ³⁵Cl and I ³⁷Cl.     

Investigations of vanadium oxide bronzes θ-(Fe1−yAly)xV2O5

The vanadium oxide bronzes θ-(Fe_1?yAl_y)_xV₂O₅ are Curie-Weiss paramagnets and hopping semiconductors. The samples studied were synthesized by direct solid-state reaction and investigated by the X-ray diffraction, differential thermal analysis, electrical resistivity, magnetic susceptibility, and Mössbauer techniques. The crystal lattice parameters, effective magnetic moments of Fe³⁺ cations, Curie-Weiss temperatures, and the values of ⁵⁷Fe hyperfine interaction parameters were determined. Endothermic effects were observed for some of the samples.     

The ESR spectrum of the C5F5 radical

Experimental results of an investigation of the ESR spectrum of the pentafluorocyclopentadienyl radical C₅F₅ in various liquid and solid matrices are reported. At temperatures above 120 K the ESR spectra indicate a five-fold symmetry with a fluorine isotropic splitting of 16 G and an isotropic g tensor of 2.0041. From liquid solutions a value A_iso¹³C ≈ 2.1 G for the isotropic coupling of the ¹³C₁ species in natural abundance was found. The ESR spectra exhibit a pronounced temperature dependence, which is interpreted by lineshape analysis to originate from an anisotropic hyperfine interaction tensor of fluoroine, partially averaged by a uniaxial rotational reorientation. From ESR spectra of polycrystalline samples the principal value A6 = 57.5–58.3 G depending on the matrix was derived.     

An AB initio molecular orbital study of the NF2 and N2F4 molecules,and ESR hyperfine coupling constants in NF2

In this publication, we present the results of gaussian type orbital calculations of ESR hyperfine coupling constants in NF₂. We also present electron density maps for the molecule, and the results of a calculation of ΔH⁰₂₉₈ for the reaction N₂F₄ → 2NF₂.     

Experimental determination of level shift and broadening by predissociation of the B3Π0· state of ICl

From the semiclassical analysis of the coupling between discrete molecular levels and continuum levels simple relations for the level shift and the level broadening are known. Laser spectroscopy on the transition is B³Π₀·?X¹Σ⁺ is applied to demonstrate the overall validity of these relations in the rotational ladder of the vibrational state υ′ = 3 of B³Π₀·. Deviations for low rotational quantum numbers might be attributed to the still unresolved hyperfine structure and the possible hyperfine predissociation and for very large rotational quantum numbers to the distortion through a coupling with a second continuum.     

The dissociation energies of gaseous Br2 and I2

New rotational analyses have been made of the B³Π_0⁺u—X¹Σ⁺_g systems of ⁷⁹Br₂, ⁸¹Br₂ and ¹²⁷I₂. The density of vibrational states near the dissociation limit in the upper states follows the LeRoy—Bernstein predictions for n = 5. From short extrapolations, the ground state dissociation energies are found to be: D₀(⁷⁹Br⁸¹Br) = 15895.6 cm^?1, D₀(¹²⁷I₂) = 12440.1 cm^?1.     

Iron-57 Mössbauer spectroscopy of Cr2TeO6 and Fe2TeO6

Iron-57 Mössbauer spectroscopy has been used to determine the hyperfine field at a chromium site in Cr₂TeO₆ which is found to be 525 kOe. The Néel temperature for Cr₂TeO₆ containing 0.4% ⁵⁷Fe is found to be 90%K; the angle θ between V_zz and the magnetic axis is 42 ± 4°. These data are compared with those for Fe₂TeO₆ where H_eff (T = 0) = 530 kOe T_N = 203°K and θ = 90°.     

The influence of cation arrangement on the EPR spectrum of Mn2+ in the spinel compounds CdB2X4

CdB₂X₄ spinels—B = Sc, Y, Lu; X = S, Se—were synthesized and their lattice constants were determined. After Mn²⁺ doping they were investigated by the EPR method over the temperature range 4.2–330 K. The temperature dependence of the hyperfine structure constant, A, was described by the ?imanek-Orbach equation and its parameters were determined. Chemical bonds in the studied spinels were characterized in more detail to obtain a linear dependence of the A constants on the modified covalency parameter.     

Laser magnetic resonance detection of rotational transitions in CH2

Laser magnetic resonance spectra observed at 163.0 μm have been identified as pure rotational transitions in the ground electronic state (³B₁) of the methylene radical. The identification was based on the observation of hyperfine spin triplets and by isotopic substitutions involving deuterium and ¹³C, as well as other chemical and spectroscopic evidence. A low-pressure flame produced by reacting discharged fluorine with methane was found to be an excellent new spectroscopic source of ground-state CH₂ radicals.     

High precision measurements of hyperfine structures near 790 nm of I 2

High precision measurements of hyperfine splittings of rovibrational lines of the (ν′-ν″)=(0–15) band of the B0 _u ⁺ — X0 _g ⁺ transition of I ₂ were performed in the near infrared around 790 nm using spectrally narrowed diode lasers. Rotational states with J″ between 0 and 99 were investigated and hyperfine parameters could be derived for the two electronic states separately. For the first time the rotational variation of the quadrupole and the spin-rotational hyperfine coupling parameters could be determined for I ₂. A relation is given, by which the hyperfine parameters for a rotational line of the (0–15) band can be predicted, and by which hyperfine splittings of this band can be calculated with an uncertainty of less than 100 kHz for 16 ≤ J″ ≤ 99.     

Hyperfine interactions in MgF2:Fe2+ and ZnF2:Fe2+ by Mössbauer spectroscopy

Measurement of the magnetic hyperfine interaction in paramagnetic Fe²⁺ in ZnF₂ and MgF₂ by Mössbauer spectroscopy is reported. The results, ?275 ± 3 kOe and ?270 ± 3 kOe for ZnF₂:Fe²⁺ and MgF₂:Fe²⁺ respectively are compared with a previous analysis of hyperfine interactions in the rutile fluorides.     

Overhauser shift in single crystals of FA2PF6

The shift ΔB_ov of the ESR line due to the saturation of the NMR of hyperfine-coupled nuclei (Overhauser shift) was measured for single crystals of the organic conductor (FA₂)^±PF₆^?. ΔB_ov is proportional to AP, where A is the average hyperfine interaction between the conduction electrons and the nuclei in resonance and P is the dynamic nuclear polarization. The proton spin relaxation times were measured from the time dependence of the Overhauser shift, ΔB_ov(t), after rf pulses.     

Microwave spectrum of aminoborane,BH2NH2

The unstable species aminoborane, BH₂NH₂, has been identified as a reaction product of ammonia with diborane by microwave spectroscopy. The rotational constants determined are A = 138212 ± 4 MHz, B = 27487.83 ± 0.10 MHz and C = 22878.44 ± 0.11 MHz for ¹¹BH₂NH₂ and A = 138199 ± 6 MHz, B = 28420.36 ± 0.11 MHz and C = 23520.78 ± 0.12 MHz for ¹⁰BH₂NH₂. The dipole moment is 1.844 ± 0.015 D.     

Investigation of the ν1−2ν2 fermi diad of OF2 by means of IR-MW double resonance

The ν₁?2ν₂ Fermi diad of OF₂ at 928 cm^?1 was investigated by IR-MW double resonance using CO₂ and N₂O lasers. Using the data of Morino (ref. 1) and the additional rotational transitions measured in this work, a partial distortion analysis of the states (1,0,0)′ and (0,2,0)′ could be carried out. The accurately determined frequencies of five IR transitions in the ν′₁ band and of two in the ν′₂ band allowed the band centres to be calculated in both cases.