33S Nuclei Research Articles

Optically-detected ENDOR of recombining shallow donors in ZnSe and CdS

Report ODENDOR spectra obtained by monitoring the ODMR signals from shallow donor centres in ZnSe and in CdS. ODENDOR signals corresponding to 33S, 77Se, 67Zn, 111Cd and 113Cd nuclei have been observed. The signals are very strong, in some cases representing 1% increase in emission intensity, and provide further conformation of the validity of the model used to describe the ODMR of donor-acceptor pairs. The 77Se and 33S ODENDOR signals provide evidence for the existence of significant chalcogen contributions to the donor wavefunction.

33S and 17O nuclear magnetic resonance study of liquid sulfur dioxide

The sulfur-33 chemical shift and 33S and 17O nmr relaxation data are reported for liquid sulfur dioxide. The 33S nucleus in SO2 is highly deshielded, 375 ± 2 ppm to high frequency of the sulfate anion. The rotational correlation time of SO2 at 294 K, 0.3 ps, is only about twice that calculated using an inertial model. The temperature dependence of the 33S and 17O nmr relaxation data can be described by an average activation energy of 6.3 ± 0.6 kJ mol−1. The effective rotational correlation time derived from 33S nmr line widths is used to calculate the 17O quadrupolar coupling constant, e2qQ/h = 6.6 ± 0.7 MHz, in SO2.

Substituent effects on the sulfur-33 chemical shift in substituted benzenesulfonic acid

Recently we reported the results of an investigation of the spin-lattice relaxation of the sulfur-33 nucleus in the sulfate and thiosulfate anions (I, 2). In the case of the thiosulfate anion only one 33S NMR signal was observed and, by synthesis of the anion with 32S in the thio position, we were able to assign the signal to the internal sulfur atom (2). The replacement of an oxygen atom in the sulfate anion by a sulfur atom to form the thiosulfate anion produces a downfield shift in the internal sulfur nucleus of 36.3 ppm (2, 3). Since so very few chemical shifts have been reported for the 33S nucleus (4), it was of interest to determine the 33S chemical shift in a series of compounds in which the chemical shift could be directly related to electron density changes on the sulfur atom. We chose as model compounds para-substituted benzenesulfonic acids. The purpose of this investigation was to explore the relationship between the 33S chemical shift and the Hammett substituent parameter (sigma) (5). From a knowledge of the electron withdrawing or donating properties of the substituents, it was hoped that the 33S chemical shifts could be used to determine if the paramagnetic term of the shielding constant dominates the chemical shift. It was also of importance to ascertain how sensitive the 33S chemical shift is to long-range electronic effects, and therefore, if 33S NMR might be chemically useful as suggested by an earlier study of thiophenes (6). The compounds used for this study were p-H, pCH3, pC1, and pN02 substituted benzenesulfonic acid obtained as reagent grade material from Kodak. A I A4 aqueous

The microwave spectrum of thioformaldehyde, CD 2S, and CH 2S: Average structure, dipole moments, and 33S quadrupole coupling

Microwave transitions up to J = 53 in the ground vibrational state of deuterothioformaldehyde, CD 2S, were studied between 8 and 40 GHz. A detailed centrifugal distortion analysis yields accurate constants for comparison with force field values. The isotopic species 13CH 2S, CH 2 34S, CH 2 33S, 13CD 2S, CD 2 34S, and CD 2 33S were studied in natural abundance. Accurate average zero-point structures were determined for both CD 2S and CH 2S: CH 2S CS=1.6138(4) CH = 1.0962(6) A ̊ ∠ HCH =116° 16(6)′, CD 2S CS=1.6136(4) CD = 1.0931(4) A ̊ ∠ DCD =116° 25(5)′ Changes in the zero-point geometry for deuterium substitution were established. Quadrupole fine structure arising from the 33S nucleus has been measured in CH 2 33S and CD 2 33S. Analysis gives the following coupling constants (for both molecules) as χ aa = −11.7 and χ bb - χ cc = 88.1 MHz. The dipole moment of CD 2S was measured to be 1.6588(8)D and an accurate comparison with CH 2S was made; the ratio of dipole moments CD 2S CH 2S was found to be 1.0062(4). The spectroscopic and bonding properties of CH 2S will be compared with formaldehyde and other molecules.

On the nature of colour centres in ultramarine and blue alkali borate glasses containing sulphur

Natural ultramarine and alkali borate glasses doped with sulphur are investigated by means of ESR and optical spectroscopy. A comparison of optical and ESR spectra makes it possible to conclude that the blue colouring (absorption band within the range 585 nm) and the anisotropic ESR signal (g1 = 2.003, g2 = 2.032, g3 = 2.051) observed both in ultramarine and alkali borate glasses doped with sulphur are conditioned by the same centres, viz. polysulphide RSn radicals. ESR studies of samples synthesized with addition of the magnetic isotope of sulphur 33S (I = 3/2) and computer calculations demonstrate that the best agreement of the theoretical spectra with experimental ones is achieved for a spin-Hamiltonian which presupposes the interaction of the unpaired electron with three magnetic 33S nuclei. It is shown using the MO LCAO method that the model of XAB radicals with nineteen valence electrons describes satisfactorily the results obtained. [Russian Text Ignored].

Higher-order effects in the EPR spectrum of F 33SO 2

The EPR spectrum of F 33SO 2, obtained by photolysis of F 2O in the presence of 33SO 2, contains additional lines whose origins are not immediately obvious. These additional lines are “forbidden” transitions which appear only because the hyperfine interactions of the 19F and 33S nuclei are almost equal, but the magnetogyric ratios differ. The presence of the extra lines shows conclusively that the 19F and 33S hyperfine interactions have the same sign.

ESR Spectroscopic Studies on the Radical Anion of [33S]‐2,2,4,4‐Tetramethylpentane‐3‐thione

Hyperfine splitting by 33S nuclei has now been recorded for the first time in the ESR spectrum of a thioketyl. The 33S‐enriched radical anion (1) shows the expected satellite signals. Judging by the spin population, (1) resembles an alkyl radical more closely than a thiyl radical. equation image

The study of the width for intermediate resonances in the 27Al(d, p) 28Al, 27Al(d, α) 25Mg, 31P(d, p) 32P and 31(d, α) 29Si reactions

The protons and α-particles from the reactions 27Al(d, p) 28Al(d, α) 25Mg, 31P(d, p) 32P and 31P(d, α) 29Si were measured and analyzed with the channel cross correlation function and auto-correlation function to determine the correlating numbers N d and average width 〈Γ μ〉. With these values, the theoretical intermediate widths were calculated to be 119 ± 30 keV in the 29Si nucleus and 249 ± 46 keV in the 33S nucleus, which were in good agreement, within the errors, with the present experimental results of 185 ± 37 keV in 29Si and 204 ± 24 keV in 33S.

Molecular constants of OCS isotopes in the (01 10) vibrational state measured by molecular-beam electric-resonance spectroscopy

The Δ J = 0, l-doublet transitions of OCS isotopes ( 16O 12C 32S, 16O 12C 33S, 16O 12C 34S, 16O 13C 32S and 18O 12C 32S) in the (01 10) vibrational state have been measured in a molecular-beam electric-resonance spectrometer equipped with a nozzle source. Rotation-vibration coupling constants and electric dipole moments have been determined for all isotopes, and the spin-rotation and the quadrupole coupling constants for the 33S nucleus in 16O 12C 33S in the υ 2=0 and υ 2=1 states.

ESR study of copper diethyldithiophosphate

ESR investigations are reported in single crystals of copper diethyldithiophosphate, magnetically diluted with the corresponding diamagnetic nickel complex. The spectrum at normal gain shows hyperfine components from 63Cu, 65Cu, and 31P nuclei. At much higher gain, hyperfine interaction from 33S nuclei in the ligand is detected. The spin Hamiltonian parameters relating to copper show tetragonal symmetry. The measured parameters are g∥ = 2.085, g⊥ = 2.025, A63Cu = 149.6 × 10−4 cm−1, A65Cu = 160.8 × 10−4 cm−1, BCu = 32.5 × 10−4 cm−1 and QCu ∞ 5.5 × 10−4cm−1. The 31P interaction is isotropic with a coupling constant AP = 9.6 × 10−4 cm−1. Angular variation of the 33S lines shows two different hyperfine tensors indicating the presence of two chemically inequivalent Cu–S bonds. The experimentally determined hyperfine constants are A 1s = 34.9 × 10−4 cm−1, B 1s = 26.1 × 10−4 cm−1, A 2s = 60.4 × 10−4 cm−1, B2s = 55.5 × 10−4 cm−1. The hyperfine parameters show that the hybridization of the ligand orbitals is very sensitive to the symmetry around the ligand. The g values and Cu hyperfine parameters are not much affected by the distortions occurring in the ligand. The energies of the d-d transitions are determined by optical absorption measurements on Cu diethyldithiophosphate in solution. Using the spin Hamiltonian parameters together with optical absorption results, the MO parameters for the complex are calculated. It is found that in addition to the σ bond, the π bonds are also strongly covalent.

Dipole Moments and Hyperfine Structure of the Group IV/VI Diatomic Molecules

Stark effect measurements on the pure rotational transitions of the Group IV/VI compounds are reported. The electric dipole moments of the molecules with the highest natural abundance were determined for the ground vibrational state. For SnS the variation of the dipole moment with vibrational state was also measured. The nuclear quadrupole hyperfine structure, which originates from the 33S and 73Ge nuclei, has been measured for nearly all of the molecules containing these nuclei. A systematic trend in the dipole moments of the Group IV/VI compounds is reported and compared with the alkali halides.

A Superhyperfine Interaction Involving 33S in the Iron-containing Proteins of Azotobacter vinelandii

Abstract A line-broadening effect attributable to 33S was observed in the asymmetrical electron spin resonance signals at g = 1.94 and 2.01 characteristic of non-heme iron proteins of Azotobacter vinelandii. The line broadening is believed to be due to unresolved superhyperfine splitting by the 33S nucleus. The observation implies an iron-sulfur interaction in at least one species of these proteins in A. vinelandii.

Investigation of the reactions 31P(n, γ) 32P and 32S(n, γ) 33S

The γ radiation following capture of thermal neutrons in 31P and 32S was investigated with scintillation-spectrometer techniques. Measurements of single and coincidence spectra and of γ-γ angular correlations yield the following spins in 32 P: J(0.52) = 0 , J(1.32) = (2), J(4.04) = 1, J(4.88) = 1, J(5.35) = 2 and J(5.78) = 1. The spins of the 1.15 and 3.26 MeV levels are confirmed to be 1 and 2, respectively. The γ-ray decay of some lower levels is determined too. In the 33S nucleus a 1.44–7.20 MeV cascade is detected. The spin and parity of the intermediate level are 3 2 + or 5 2 + . However, the existence of a level at about 1.4 MeV, expected on basis of a shell-model calculation, cannot be proved. In a sum-coincidence measurement a few other two-step cascades are detected.