Electron spin resonance spectra of two naturally occurring paramagnetic centres in diamond

A centre, characterised by an isotropie singlet at g = 2.000 and satellite lines having the correct relative intensity for ²⁹Si hyperfine features, has been detected in natural diamond. The form of the ²⁹Si hyperfine tensor suggests that the electronic structure of this silicon centre is similar to that of the common nitrogen centre. Although silicon is an expected impurity in diamond, paramagnetic centres containing it have not previously been reported. We have also detected the paramagnetic nitrogen centre previously reported, characterised by a hyperfine triplet with $\text{A}{}_6\text{(}{}^{14}\text{N) = 7.5G}$ and $\text{A}{}_{\mathrm{\perp }}\text{(}{}^{14}\text{N) = 5.0 G}$. This centre was accompanied by the common nitrogen centre in only one case. Other naturally occurring centres, apparently comprising two weakly coupled electrons in triplet states, were too poorly defined to characterise fully.     

Measurement of line widths of CO of planetary interest at low temperatures

Self-broadened, air-broadened and CO₂-broadened half-widths of lines R(0) through R(0) in the CO fundamental have been measured at 100°K (self-broadening only), 200°K, 250°K and 300°K using the Ladenburg-Reiche curve-of-growth. The relation $\text{γ}{}^{\mathrm{°}}{}_{\mathrm{m}}\text{(T)}\text{γ}{}^{\mathrm{°}}{}_{\mathrm{m}}\text{(300°K)}\text{=(}\text{300}\text{T}\text{)}{}^{0.75}$, which we found previously for the nitrogen-broadened half-widths of R(0), R(8) and R(16), is shown to be valid for all of the line widths measured in the present study.     

Low temperature specific heats of nearly one-dimensional antiferromagnet: CuCl2·2NC5H5

Transition temperature to LRO state was found at T_N=1.14K for nearly one-dimensional antiferromagnet CuCl₂ · 2NC₅H₅. Intra- and inter-chain exchange constants J and J′ were estimated, $\text{kT}{}_{\mathrm{<mtext>N</mtext>}}\text{J}\text{=0.082}$ and $\text{J′}\text{J}\text{=3×10}{}^{\mathrm{?3}}$, respectively. Comparison with those of TMMC implies highly one-dimensional character.     

Infrared optical properties of MoSe2

The infrared absorption spectrum of a single crystal of MoSe₂ is reported. A damped oscillator fit to the fundamental band gives the transverse optic frequency, $\text{Ω}{}_{\mathrm{TO}}\text{= 277}\text{cm}{}^{-1}$ at 300° K and $\text{Ω}{}_{\mathrm{TO}}\text{= 283}\text{cm}{}^{-1}$ at 77° K. The static and high frequency dielectric constants have been determined as K_s = 16.81 and K_∞ = 10.24 respectively. An absorption band appears in the i.r. spectrum at 482 cm^-1, and has been attributed to the oxygen impurity in the crystal.     

Magnetic phase transitions,anisotropic susceptibility and dipolar interactions in antiferromagnetic MnNb2O6

The magnetic properties of MnNb₂O₆ single crystals have been studied in the temperature range 1.6–300 K (T_N = 4.4 K), in fields up to 220 kOe. The high field saturation at low temperature, as well as the paramagnetic susceptibility at high temperature, agree well with a ${}^6\text{S}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ state for Mn²⁺ ions. From 1.6 to 3.8 K a spin flop is induced by fields ranging from 17 to 21 kOe, applied in the direction of the a-axis. Elements of the magnetic susceptibility tensors up to rank 12, measured below the spin flop field, are in accordance with a magnetic anisotropy originating mainly from magnetic dipolar interactions.     

A study of 3He capture in light nuclei

Excitation functions at θ = 90° have been measured for ${}^{16}\text{O}\text{(}{}^3\text{He}\text{, γ}{}_{\mathrm{0?2,\; 3?5,\; 6}}\text{)}{}^{19}\text{Ne}$, ${}^{15}\text{N}\text{(}{}^3\text{He}\text{, γ}{}_{\mathrm{0,\; 1?4}}\text{)}{}^{18}\text{F}\text{,}{}^{14}\text{N}\text{(}{}^3\text{He}\text{, γ}{}_{\mathrm{0,\; 1,2,3}}\text{)}{}^{17}\text{F}$, and ${}^{20}\text{Ne}\text{(}{}^3\text{He}\text{, γ}{}_{\mathrm{0\; +\; 1}}\text{)}{}^{23}\text{Mg}$, in the range E_{3He = 3–19 MeV}. The first reaction has also been studied at θ = 40°. Excitation functions at 90° have also been measured for and ${}^4\text{He}\text{(}{}^3\text{He}\text{, γ}{}_{\mathrm{0\; +\; 1}}\text{)}{}^7\text{Be}$ for E_3He = 19–26 MeV. Angular distributions have been measured for the first four reactions.For the most excitation functions, a broad peak is observed, several MeV wide, centred at about E_x≈ 20 MeV. Superimposed on this, in some cases, are narrower peaks, with width ≈ 1 MeV. Energies and widths have been extracted for all resonances.Cluster-model calculations have been carried out, using methods similar to those which have proved successful for low-lying states in A= 18–19 nuclei. No satisfactory correspondence with the present results was found. The shell model has been used to calculate Γ_3He and Γ_γ for 1?ω excitations in the final nuclei. These generally show good agreement with the trends of the experimental data. The results are consistent with the excitation of the giant dipole resonance in ³He capture, but much more weakly than in proton capture.     

Structure,vibrational study and conductivity of the trihydrated uranyl bis(dihydrogenophosphate): UO2(H2PO4)2·3H2O

The X-ray structure (293 K) of UO₂(H₂PO₄)₂·3H₂O has been refined (R = 0.062): M_r = 518g, space group: P2₁/c (Z = 4); $\text{a = 10.816(1)}\text{A}\text{?}$, $\text{b = 13.896(2)}\text{A}\text{?}$, $\text{c = 7.481(1)}\text{A}\text{?}$, β = 105.65(1)^°, $\text{V = 1082.7(2)}\text{A}\text{?}{}^3$; D_c = 3.17 Mg m^?3. The structure consists of infinite chains along the (101) axis with U atoms bridged by two H₂PO₄ groups. The U atom is surrounded by a pentagonal bipyramid of oxygen atoms, one of them being an equatorial water molecule. The cohesion between the chains is ensured by hydrogen bonds involving the two last water molecules. An assignment of IR and Raman bands with isotopic substitution spectra is proposed. A phase transition at 128 K was made evident by DSC and spectroscopy. The room-temperature phase is characterized by a high disorder of the OH bond orientation while in the low-temperature phase H₂O and POH species appear well oriented. The conductivity seems to occur by proton transfer and protonic-species rotation at the POH-water molecular interface between the chains. ac conductivity has been determined by means of the complex-impedance method ($\text{σ}{}_{\mathrm{<mtext>RT</mtext>}}\text{～ (3?12) × 10}{}^{\mathrm{?5}}\text{Ω}{}^{\mathrm{?1}}\text{cm}{}^{\mathrm{?1}}$; E ～ 0.20 eV).     

Polarizabilities of shallow donors in silicon

Capacitance measurements on N-type As, P, and Sb-doped Si samples have been made between 4.2 and 1.35°K, from 0.3 to 100 kHz as a function of (N_D ? N_A) [high purity to 2.7 × 10¹⁸/cm³]. From the dielectric constant variation with (N_D ? N_A) donor polarizabilities α_AS, α_P, and α_Sb are found respectively to be $\text{1.0±0.1, 2.4±0.4,}\text{and}\text{3.1±0.3 × 10}{}^5\text{A}\text{?}{}^3$.     

Nonorthogonality corrections in the method of correlated basis functions

A set of normalized linearly independent basis functions φ₁, φ₂, …, φ_j, … generates matrix representatives $\text{H}$ and $\text{N}$ of the Hamiltonian operator and the identity. An orthonormal basis $\text{φ}{}_1$, $\text{φ}{}_2$, …, $\text{φ}{}_{\mathrm{j}}$, … generated by a Löwdin transformation is characterized by the distance in Hilbert space between $\text{φ}{}_{\mathrm{j}}$ and φ_j. The choice of positive definite $\text{N}$${}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ minimizes these distances and maximizes the diagonal elements of $\text{N}$${}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$. Again for positive definite $\text{N}$${}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and a finite basis, 1 ? j ? p, the analysis yields a general theorem on Trace $\text{N}$${}^{\mathrm{<mtext>?n</mtext><mtext>2</mtext>}}$ (? p for all positive and negative integral values of n except n = ?1 and ? p for n = ?1).Sufficient conditions are determined which permit the application of the binomial theorem to the evaluation of the transform of $\text{H}$. Approximate formulas for the energy eigenvalues through third order in nondiagonal matrix elements are presented in a compact form containing characteristic nonorthogonality corrections depending on the exterior or interior location of the matrix element in the perturbation formulas.     

A study of the excited electronic states of 9-fluorenone

Some spectroscopic properties of the low-energy electronic states of 9-fluorenone have been examined. The spectra in paraffin matrices at 4.2°K show detailed vibrational spectra. Two fluorescence spectra are observed; a diffuse emission arises from 9-fluorenone crystals in the paraffin matrix, and a sharp emission is characteristic of the molecule. The sharp fluorescence is analyzed in terms of known a₁ vibrational fundamentals. The sharp absorption is a near mirror-image to the fluorescence, so Herzberg-Teller vibrations are not prominent. The polarization in the crystal spectrum allows this low-energy transition near 23 000 cm^?1 to be assigned ${}^1\text{B}{}_2\text{←}{}^1\text{A}{}_1$. Because there is no vibronic perturbation in fluorescence, and certainly no out-of-plane modes, a $\text{π}{}^1\text{← n}$ transition seen at about 26 000 cm^?1 is tentatively assigned ${}^1\text{B}{}_1\text{←}{}^1\text{A}{}_1$. Another sharp absorption system is seen at 31 000 cm^?1 in the paraffin matrices at 4.2°K (linewidth 6 cm^?1) but no fluorescence was detected. The polarized crystal spectrum indicated the assignment of this system and another very strong system at 40 000 cm^?1 to be ${}^1\text{B}{}_2\text{←}{}^1\text{A}{}_1$, while other systems at about 34 000 cm^?1 and 44 000 cm^?1 are ${}^1\text{A}{}_1\text{←}{}^1\text{A}{}_1$.The phosphorescence spectrum of pyrene-d₁₀ held in a single crystal of 9-fluorenone at 4.2°K has been recorded. No delayed fluorescence from the host crystal is observed at 4.2°K but is intense at 77°K. The energy difference between host and guest triplet levels is estimated to be about 900 cm^?1 allowing the lowest triplet state of 9-fluorenone to be placed at 17 800 cm^?1.     

Magnetization,magnetocrystalline anisotropy,magnetostriction and elastic constants of the Heusler alloy: Cu2Mn Al

Three kg of stoichiometric single crystals of Cu₂Mn Al have been grown by the Bridgman method. The thermal variations of their magnetization, anisotropy, magnetostriction and elastic constants have been measured between 4.2 and 300 K. This alloy exhibits a small magnetocrystalline anisotropy, but a large elastic anisotropy $\text{(}\text{C}{}^{\mathrm{?}}\text{C}{}^{\mathrm{\gamma }}\text{= 4.9)}$ which explains the strong anisotropy of the magnetostriction $\text{(}\text{λ}{}^{\mathrm{\gamma ,2}}\text{λ}{}^{\mathrm{?,2}}\text{= 10)}$. The magnetic moment per Mn atom at 0 K is 3.6 μ_B.     

The interaction of 33 MeV polarised helions with 30Si

Distributions of cross sections and analysing powers have been measured over the range ～ 14°–100° c.m. for the $\text{(}{}^3\text{H}\text{,}{}^3\text{He), (}{}^3\text{H}\text{,}{}^4\text{He), (}{}^{\mathrm{<mtext>3</mtext><mtext>H</mtext>}}\text{,}{}^2\text{H)}$ reactions at 33.4 MeV incident e using a ～ 95 % enriched ³⁰Si target. Phenomenological optical-model analyses of the elastic-scattering data have been carried out. A DWBA analysis of the inelastic-scattering data for the 2.24 MeV (2⁺) and 5.49 MeV (3^?) states of ³⁰Si has yielded values of the deformation β₂ and β₃. The j-dependence of the analysing powers for the (³He, ⁴He) and (³He, ²H) reactions has identified the 6.71 MeV level of ²⁹Si as a $\text{5}\text{2}{}^{\mathrm{+}}$ state, and a level near 9.5 MeV in ³¹P as a possible $\text{7}\text{2}{}^{\mathrm{?}}$ state. Spectroscopic factors for ten states in ²⁹Si and seven states in ³¹P have been deduced and are compared with other work. The extent to which the data defines the ³He spin-orbit potential is discussed.     

Electronic conductivity of AgI using D.C. polarization and charge transfer techniques

A Study of electronic conductivity using the d.c. polarization technique has been carried out in α and β-AgI which shows the former is a hole and the latter an electron conductor. Activation energies of undoped and Cu-doped single crystals and polycrystalline β-AgI were found to be 0.46 eV, 0.34 eV and 0.44 eV respectively and can be related to electron trap depths. The electron transference number ($\text{σ}{}_{\mathrm{\theta }}\text{σ}{}_{\mathrm{t}}$) for polycrystalline β-AgI was found to be 0.008 at 306 K. The activation energy for hole conduction in α-AgI was determined to be 0.97 eV in agreement with previous XPS studies.Transient measurements have also been conducted using the charge transfer technique in double cells of polycrystalline β-AgI. The carrier concentration C_θ and electron mobility μ_θ, have thus been estimated to be 1.8 × $\text{10}{}^{15}\text{cm}{}^3$ and 5.14 × 10^?5$\text{cm}{}^2\text{V}$?sec. respectively at 306 K, while the double layer capacitance was 0.496 $\text{μF}\text{cm}{}^2$.     

Teopия acиммeтpии штaкoвcкиx пpoфилeй вoдopoдныx линий в плoтнoй плaзмe

The asymmetric Stark profile for spectral lines of hydrogen has been calculated in first approximation in terms of the expansion parameter $\text{n}{}^2\text{a}{}_0\text{R}{}_0$ [a₀=Bohr radius, n= principal quantum numberm $\text{R}{}_0\text{=(}\text{3}\text{4πN}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}$=mean distance between charged particles]. Additional terms, which determine the asymmetry, are expressed through the universal functions Λ(β) and χ(β), which are connected with the first moments of the components of the ion-electric field inhomogeneity tensor. Comparison is made with results based on a nearest neighbour approximation. It is shown that the shift of the symmetry centre of the profiles may be the ion-electric field inhomogeneity.     

Thermochemistry of azide salts and the azide ion using direct minimisation equations to obtain the lattice energy of the univalent azide salts

The opportunity to test a new equation for the computation of the lattice energy and at the same time examine a disparity in the literature data for the enthalpy of formation of the azide ion, $\text{ΔH}{}^{\mathrm{\theta }}{}_{\mathrm{?}}\text{(}\text{N}{}_3{}^{\mathrm{?}}\text{) (}\text{g}\text{)}$ was the motivation for this study. The results confirm our earlier calculation and show the new equation to be reliable. Thermodynamic data produced in the study take values: $\text{ΔH}{}^{\mathrm{\theta }}{}_{\mathrm{?}}\text{(}\text{N}{}_3{}^{\mathrm{?}}\text{)(}\text{g}\text{) = 144}\text{kJ mor}{}^{\mathrm{?1}}$ΔH^θ_hyd(N₃^?) = ?315 KJ mol^?1 or ΔH^θ_hyd(N₃^?) = ?295 KJ mol^?1U_POT(NaN₃) = 732 kJ mol^?1U_POT(KN₃) = 659 kJ mol^?1U_POT(RbN₃) = 637 kJ mol^?1U_POT(CsN₃) = 612 kJ mol^?1U_POT(TIN₃) = 689 kJ mol^?1. The lattice energies of azides whose enthalpies of formation are documented have been calculated as well as the enthalpy of formation of the azide radical.     

EPR study of the E′4 center in α-quartz

Electron paramagnetic resonance measurements of the E′₄ center in α-quartz have now proven that this species contains one unpaired electron ($\text{S=}\text{1}\text{2}$), with hyperfine splitting from one proton ($\text{I=}\text{1}\text{2}$). The spin-Hamiltonian matrices $\text{g}$ and $\text{A}\text{(H}{}^1\text{)}$ have been measured at room temperature.     

Polarization transfer effects in (p, n reactions on light nuclei at θ = 0°

Transverse polarization transfer coefficients K_y^y′ have been measured at a reaction angle of 0° for the reactions ${}^9\text{Be}\text{(}\text{p}\text{,}\text{n}\text{)}{}^9\text{B}\text{,}{}^{11}\text{C}$ and ${}^{13}\text{C}\text{(}\text{p}\text{,}\text{n}\text{)}{}^{13}\text{N}$. In the energy range covered by these measurements, i.e., from about 7 to 15 MeV, the K_y^y′(0) values are generally positive. The polarization transfer excitation functions all show considerable structure which we largely attribute to compound nucleus effects.     

Electrical and structural properties of iron-doped β-alumina

β-alumina containing 50 w/o Fe exhibits high electronic conductivity when sintered in air but Mössbauer studies have shown the presence of Fe₃O₄. Single-phase β-alumina containing 50 w/o Fe could be prepared by sintering at 1400°C for 4–4.5 h followed by annealing at 1300°C for 96 h encapsulated with coarse β-alumina powder enriched with Na₂CO₃. Mössbauer spectroscopy indicated that all iron was present as Fe(III). Complex-plane impedance data showed a maximum bulk $\text{σ}{}_{\mathrm{25°C}}\text{= 5.56 × 10}{}^{-4}\text{(Ω cm)}{}^{-1}$ with little electronic conductivity. Reduction treatments on Fe-doped β-alumina utilizing H₂:N₂ gas were successful in producing a mixed conductor containing Fe(II) and Fe(III) but also produced a distorted β-alumina lattice. This material exhibited an electronic conductivity $\text{σ}{}_{\mathrm{e,25°C}}\text{= 2 × 10}{}^{-4}\text{(Ω cm)}{}^{-1}$ and a bulk ionic conductivity $\text{σ}{}_{\mathrm{b,25°C}}\text{= 1.35 × 10}{}^{-4}\text{(Ω cm)}{}^{-1}$.     

N2+ bound quartet and sextet state potential energy curves

Potential energy curves for the ${}^4\text{Σ}{}^{\mathrm{+}}{}_{\mathrm{u}}$, ${}^4\text{Π}{}_{\mathrm{g}}$ and ${}^6\text{Σ}{}^{\mathrm{+}}{}_{\mathrm{g}}$ states of N⁺₂ that dissociate to N (${}^4\text{S}{}^0$) and $\text{N}{}^{\mathrm{+}}\text{(}{}^3\text{P)}$, have been determined from a complete active space self-consistent field calculation. The ${}^6\text{Σ}{}^{\mathrm{+}}{}_{\mathrm{g}}$ state is found to be significantly bound (D_e = 2.68 eV) with a minimum at 1.72 Å.     

Hydrogen detection by SIMS: Hydrogen on polycrystalline vanadium

The interaction of hydrogen with polycrystalline vanadium has been studied by SIMS and flash-desorption. Two well defined vanadium surfaces with different amounts of residual oxygen were exposed to H₂-doses up to 1000 L. The investigations were carried out under UHV conditions. The experiments result in a better understanding of the vanadium-hydrogen interaction, especially with regard to the influence of residual oxygen. The residual oxygen concentration can be characterized by the O^? emission; it increases with the number of O₂ exposure/ heating cycles. Different groups of secondary ions and flash signals, characteristic of certain chemical environments of hydrogen, could be distinguished. The ratios $\text{VH}{}^{\mathrm{+}}\text{V}{}^{\mathrm{+}}$ and $\text{V}{}_2\text{H}{}^{\mathrm{+}}\text{V}{}^{\mathrm{+}}{}_2$ proved to be typical of the direct V-H bond concentration. This can be derived from their behaviour during H₂ and O₂ exposure, e.g. Bulk dissolved hydrogen is indicated by a dosedepending H₂ flash signal at 900 K. Bulk solution of H₂ is blocked by a monomolecular oxygen layer. An additional H₂ flash signal at 500 K together with increasing values of $\text{VH}{}^{\mathrm{+}}\text{V}{}^{\mathrm{+}}$ and $\text{V}{}_2\text{H}{}^{\mathrm{+}}\text{V}{}^{\mathrm{+}}{}_2$ is observed for relatively oxygen free targets after H₂ exposure. The detection limit for metal-bonded hydrogen was found to be less than 100 ppm of one monolayer.