The measurement of the rotational relaxation times of OCS from the nutation signals

The time dependence of microwave absorption was measured for the J = 2-1 and J = 3-2 transitions of OCS under on- and off-resonant conditions utilizing Stark and source modulation, respectively. The two effective pressure parameters obtained under the two conditions, which correspond to $\text{(T}{}_2{}^{\mathrm{?1}}\text{+ T}{}_1{}^{\mathrm{?1}}\text{)}\text{4πP}$ and $\text{(2πT}{}_2\text{P)}{}^{\mathrm{?1}}$, respectively, according to the Bloch equation, are different beyond experimental error; the difference $\text{(T}{}_2{}^{\mathrm{?1}}\text{? T}{}_1{}^{\mathrm{?1}}\text{)}\text{2πP}$ is 0.94 ± 0.38 (2.5σ) MHz/Torr for J = 2?1. This difference was also determined to be 1.19 ± 0.30 MHz/Torr from the dependence of the nutation frequency on the microwave power.     

Non-analyticity of the entropy and Nernst's law in random spin systems

It is shown explicitly for a soluble model that a random spin system can have an entropy which is non-analytic at (H = 0, T = 0), with $\text{(}\text{?S}\text{?H}\text{)}{}_{\mathrm{H=0}}$ and/or $\text{(}\text{?}{}^2\text{S}\text{?H}{}^2\text{)}{}_{\mathrm{H=0}}$non-vanishing in the T → 0 limit, while nevertheless Nernst's law is satisfied.     

Low-temperature electron radiation damage in scandium

Electron irradiation of hcp scandium at T ? 12 K allowed to determine the energy threshold for Frenkel-pair creation, T_d = 13.8 ± 0.5 eV, and the defect resistivity, $\text{?}{}_{\mathrm{<mtext>F</mtext>}}\text{≈ 5 × 10}{}^{\mathrm{?3}}\text{Ω}\text{cm/F.P}$. The annealing spectrum exhibits four substages between 20 and 70 K, a broad substage centered at 105 K attributed to interstitial long-range migration, and a stage III between 240 and 300 K.     

Critical slowing down of fluctuations in squaric acid (H2C4O4) at the phase transition observed by 13C spin-lattice relaxation

Spin lattice relaxation T₁ of naturally abundant ¹³C nuclei in squaric acid was measured close to the antiferroelectric-paraelectric phase transition temperature T_c = 373 K. A rapid increase in $\text{1}\text{T}{}_1$ is observed close to T_c coming from above, which follows the power law $\text{1}\text{T}{}_1\text{～ ε}{}^{\mathrm{?1.4}}$ where $\text{ε =}\text{(T ? T}{}_{\mathrm{c}}\text{)}\text{T}{}_{\mathrm{c}}$. This behaviour is explained on the basis of the two-dimensional character of the fluctuations.     

Hopping conductivity in amorphous carbon films

The electrical resistivity of amorphous carbon films getter-sputtered at 95°K is well fitted between 300 and 20°K by the relation $\text{? = ?}{}_0\text{exp}\text{[(T}{}_0\text{/T)}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{]}$ with T₀ ? 7 × 10⁷K. This behavior suggests a hopping conductivity very similar to that found in other amorphous semiconductors.     

Electron spin relaxation of irradiated ferroelectric KDP: K2SeO4

Electron spin resonance relaxation times were measured for the radiation induced radical ion SeO₄^3? in selenium doped KDP single crystals. The spin-lattice relaxation time was found to obey the relation $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>R</mtext>}}{}^{\mathrm{?1}}\text{= AT + BT}{}^5\text{∫}{}_0{}^{\mathrm{<mtext>\theta </mtext><mtext>2T</mtext>}}\text{x}{}^4\text{csch}{}^2\text{x}\text{d}\text{x}$ from 7 K to 200 K except in the neighborhood of the transition temperature where the data fit the expression T₁^?1 = T_1R^?1b_±T ? T_c^m± where θ is the Debye temperature and the plus and minus signs refer to data at temperatures above and below T_c respectively.     

The law of corresponding states for metals

Using the similarity of the effective potentials seen by ions in metals a reduced phonon equation of state is derived. It is shown that the melting point T_m(0) and the atomic volume Ω₀ at T = 0 K and at p = 0 are suitable macroscopic parameters for scaling ? and σ characterizing the interatomic potentials of metals having similar structures. The temperature and pressure dependence of thermodynamical quantities reduced with the above parameters are discussed and the results are compared with the experiment. It is shown that the pressure dependence of the reduced thermodynamic quantities can be described by the pressure dependence of the scaling parameters T_m(p) and Ω₀(p).The general form of the reduced equation of state (containing the electronic contributions as well) obtained gives that the reduced pressure is a universal function of the following reduced variables: the volume, temperature, de Broglie wavelength, Gibbs free energy of electrons $\text{3}\text{5}\text{zE}{}_{\mathrm{fo}}\text{?}$ (E_fo is the Fermi energy at T = 0 K) and depe of the valence z as well. It is shown that $\text{E}{}_{\mathrm{fo}}\text{?}$ is a function of $\text{Ω}{}_{\mathrm{o}}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}$ and $\text{(}\text{E}{}_{\mathrm{fo}}\text{/?}\text{)Ω}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ is approximately constant within the same sub-group of the periodic table.     

Magnetic order induced birefringence and critical behaviour of the long range order parameter in NiO

The optical linear magnetic birefringence of single-domain NiO crystals was measured at temperatures above and below the antiferromagnetic phase transition. The analysis of the experimental data yield a Néel temperature of T_N = (523.7 ± 0.2)K and a critical exponent β = 0.325^+0.01_-0.02 which determines the temperature behaviour of the magnetic long range order parameter $\text{S}\text{?}\text{～ (}\text{1?T}\text{T}{}_{\mathrm{N}}\text{)}{}^{\mathrm{\beta }}$. This critical behaviour of S? is found to be continued to temperatures well below T_N.     

Synchrotron X-ray study of physisorbed films of mixtures of Ar and Xe on graphite

Mixtures of Ar and Xe have been studied in most of the sub-monolayer region of the phase diagram (T ,χ, ?), T = temperature, χ = chemical composition, ? = fraction of a monolayer. The basic feature is a large tendency to form $\text{3}\text{×}\text{3}$ commensurate alloys (Kr-like structures), but none of the commensurate nor of the incommensurate structures form a chemically ordered alloy at 11K. Thus the 2D solid can be thought of as a solid consisting of particles of an average size. This allows us to study the commensurate-incommensurate phase transition driven by average particle size. The transition is indeed a sharp first order transition taking place through coexisting phases $\text{(τ}{}_{\mathrm{<mtext>A</mtext>}}\text{= 1.64}\text{A}\text{?}{}^{\mathrm{?1}}$ and $\text{τ}{}_{\mathrm{<mtext>B</mtext>}}\text{= 1.703}\text{A}\text{?}{}^{\mathrm{?1}}\text{)}$, as was the case for the low temperature pure Kr system [1]. Another interesting feature is the existence of well correlated liquid-like structures which preserve their correlation over a temperature range of 5 K or more. This unusual behaviour is for chemical compositions where there is coexistence of a commensurate and an incommensurate solid at high temperature.     

Pressure dependence of dielectric constants of alums

The effect of hydrostatic pressure p on the low frequency dielectric constant ? has been investigated for 31 alums of different composition at 293 K in the pressure range between 0 and 7 kbar. The ?(p)-curves deviate from linearity. For almost all alums with symmetric ions the first-, second-, and third-order pressure derivatives of the dielectric constant obey the following relations:

$\text{(}\text{??}\text{?p}\text{)}{}_{\mathrm{T}}\text{< 0, (}\text{?}{}^2\text{?}\text{?p}{}^2\text{)}{}_{\mathrm{T}}\text{> 0, and (}\text{?}{}^3\text{?}\text{?p}{}^3\text{)}{}_{\mathrm{T}}\text{< 0}$

. The logarithmic volume derivative of the low frequency polarizability, $\text{(}\text{? ln α}\text{? ln V}\text{)}{}_{\mathrm{T}}$, is found to be quasi-invariant also in the isotypic crystal group of alums (Jarman's rule). For the cases, where piezooptical data are available, the optical and infrared contributions to the volume dependence of the polarizability are determined.     

Oscillator strengths in the Cameron system of carbon monoxide

Relative oscillator strengths in the Cameron system of CO(a³Π ← X¹Σ) have been observed in absorption for six bands (υ′ = 0–5, υ″ = 0) with the result, normalized to the absolute (0, 0) band measurement of Hasson and Nicholls, $\text{?}{}_{00}\text{= (1.62±0.07) × 10}{}^{\mathrm{?7}}$, $\text{?}{}_{10}\text{= (1.96±0.09) × 10}{}^{\mathrm{?7}}$, $\text{?}{}_{20}\text{= (1.41±0.04) × 10}{}^{\mathrm{?7}}$, $\text{?}{}_{\mathrm{3\; 0}}\text{= (0.72±0.03) × 10}{}^{\mathrm{?7}}$, $\text{?}{}_{40}\text{= (0.31±0.02) × 10}{}^{\mathrm{?7}}$, $\text{?}{}_{50}\text{= (0.14±0.01) × 10}{}^{\mathrm{?7}}$. The density of CO was modulated with a motor-driven vacuum valve and synchronous fluctuations (?1 per cent) in the transmitted intensity detected with a lock-in amplifier. Peak pressure in the 21 cm absorption cell was approximately 10 torr. A curve of growth analysis was used to correct saturation effects by less than 3 per cent.     

Investigation of the central component of SrTiO3 by neutron scattering with eV resolution

We studied the energy width and the width in reciprocal space Δq of the central mode of SrTiO₃ above T_c. At T_c+4° we observed an energy width of about 6×10^?7 eV. If the measured Δq is interpreted by a correlation length $\text{Δq}{}^{\mathrm{?1}}\text{= ξ = ξ}{}_0\text{?}{}^{\mathrm{<mtext>?</mtext><mtext>2</mtext><mtext>3</mtext>}}$ we obtain $\text{ξ}{}_0\text{= 75}\text{A}\text{?}$.     

Temperature and pressure dependence of the elastic property of GeS2 glass

The sound velocities in GeS₂ glass have been measured by means of ultrasonic interferometry as a function of temperature or pressure up to 1.8 kbar. The bulk modulus K_s = 117.6 kbar and shear modulus G = 60.60 kbar were obtained for GeS₂ glass at 15°C and 1 atm. The temperature derivatives of both sound velocities and elastic moduli are negative :

$\text{(}\text{?ν}{}_1\text{?T}\text{)}$

_p =

$\text{?1.54 × 10}{}^{\mathrm{?4}}\text{km}\text{sec}$

°C,

$\text{(}\text{?ν}{}_1\text{?T}\text{)}$

_p =

$\text{?1.27× 10}{}^{\mathrm{?4}}\text{km}\text{sec}$

°C and

$\text{(}\text{?K}{}_{\mathrm{s}}\text{?T}\text{)}$

_p =

$\text{?1.27 × 10}{}^{\mathrm{?2}}\text{kbar}\text{°C}$

,

$\text{(}\text{?G}\text{?T}\text{)}$

_p = ?1.23 × 10^?2 kbar/°C,

$\text{(}\text{?Y}\text{?T}\text{)}$

_p = ?2.93 × 10^?2 their pressure derivatives are positive:

$\text{(}\text{?ν}{}_1\text{?P}\text{)}$

_T = 4.43× 10^?2km/kbar,

$\text{(}\text{?ν}{}_1\text{?P}\text{)}$

_T =

$\text{0.633 × 10}{}^{\mathrm{?2}}\text{km}\text{kbar}$

and (?K_s?P0)_T=6.81,

$\text{(}\text{?G}\text{?P)}{}_{\mathrm{T}}$

= 1.03, (?Y?T_T= 3.57. The Grüneisen parameter, γ_th= 0.298, and the second Grüneisen parameter, δ_s = 3.27, have also been calculated from these data. The elastic behavior of GeS₂ glass has proved to be normal despite the structural similarity among the tetrahedrally coordinated SiO₂, GeO₂ and GeS₂ glasses.     

Nuclear spin-lattice relaxation of Co59 in CoB

We report the result of the Co⁵⁹ nuclear spin-lattice relaxation time T₁ measurements in the diamagnetic monoboride CoB. The analysis of the data, in the 4.2–300 K temperature range, allows us to separate three contributions to the relaxation rate: first a Korringa process, (T_1KT)^?1= 0.21 sec^?1K^?1 (in good agreement with the temperature independent isotropic Knight shift) from which we deduced the Co⁵⁹ hyperfine constant A=6.2 ×10^?6eV, second an impurity contribution independent of temperature and third a quadrupolar term, $\text{T}{}^{\mathrm{?1}}{}_{\mathrm{1Q}}\text{=3560 (}\text{T}\text{θ}{}_{\mathrm{D}}\text{)}{}^2\text{E(}\text{T}\text{θ}{}_{\mathrm{D}}\text{) sec}{}^{\mathrm{?1}}$, which is predominant at high temperature and well explained by the Van Kranendonk theory. It seems that it was the first time that such a quadrupolar effect was detected in a metallic compound. A remarkable coherency between Lundquist's three bands model and our experimental results has to be noted.     

Analysis of the 2770-Å emission system in I2

A weak emission spectrum of I₂ near 2770 Å is reanalyzed and found to to minate on the A(1u³Π) state. The assigned bands span v″ levels 5–19 and v′ levels 0–8. The new assignment is corroborated by isotope shifts, band profile simulations, and Franck-Condon calculations. The excited state is an ion-pair state, probably the 1g state which tends toward $\text{I}{}^{\mathrm{?}}\text{(}{}^1\text{S) +}\text{I}{}^{\mathrm{+}}\text{(}{}^3\text{P}{}_1\text{)}$. In combination with other results for the A state, the analysis yields the following spectroscopic constants: T″_e = 10 907 cm^?1, $\text{D}$″_e = 1640 cm^?1, ω″_e = 95 cm^?1, $\text{R″}{}_{\mathrm{e}}\text{= 3.06}\text{A}\text{?}$; T′_e = 47 559.1 cm^?1, ω′_e = 106.60 cm^?1, $\text{R′}{}_{\mathrm{e}}\text{= 3.53}\text{A}\text{?}$.     

Study by brillouin scattering of the C33 constant of thiourea submitted to an electric field

The C₃₃ constant is discontinuous for the lock-in transition at T₁ = 169 K. The variation ΔT₁ of the temperature of transition is a linear function of the applied electric field E and we find $\text{d}\text{T}{}_1\text{d}\text{E}\text{=0.82 deg.cm kV}{}^{\mathrm{?1}}$.Above a mean field E = 10 kV cm^?1 the transition observed for a first heating spreads on several degrees because damages appear in the incommensurate phase and the electric field becomes inhomogeneous.The results obtained at low fields are in very good accordance with the value of $\text{d}\text{T}{}_1\text{d}\text{E}$ calculated from the Clapeyron formula.Taking into account of the incommensurability of the phase above T₁, it can be shown that

$\text{dT}{}_1\text{dE}\text{=}\text{C}\text{2πP}{}_{\mathrm{o}}\text{3}\text{3}\text{?}\text{2}$

The knowledge of the spontaneous polarisation P₀ gives for the Curie constant C = 2.1 × 10³ K in qualitative agreement with the value deduced from measurements of the dielectric constant in the ferroelectric direction.     

Optical detection of cyclotron resonance of electron and holes in CdTe

Cyclotron resonance of electron and holes have been optically detected at 70 GHz and at 1.8 K in n-type CdTe. The bare effective masses, in unit of the free electron mass, are found to be: $\text{m}{}^1\text{= 0.088 ± 0.004}$, $\text{m}{}^1{}_{\mathrm{lh}}\text{= 0.12 ± 0.01}$, $\text{m}{}^1\text{= 0.60 ± for H // <100>}$, and $\text{m}{}^1{}_{\mathrm{e}}\text{= 0.089 0.004}$, $\text{m}{}^1{}_{\mathrm{lh}}\text{= 0.11 ± 0.01}$, $\text{m}{}^1{}_{\mathrm{hh}}\text{= 0.69 ± 0.02}$ for H // <111>. The Luttinger valence band parameters deduced from these measurements are: γ₁ = 5.3 ± 0.5, γ₂ = 1.7 ± 0.3 and γ₃ = 2.0 ± 0.3, in fair agreement with the calculations of Lawaetz.     

Study of the three-proton three-neutron-hole nucleus 208At

Levels in ²⁰⁸At were populated in the ²⁰⁹Bi(α, 5n) reaction, and the subsequent radiation was studied using γ-spectroscopic methods including γ-ray excitation function and angular distribution, γγ(t) coincidence and γt measurements, as well as measurements of conversion electrons. The excited spectrum of ²⁰⁸At is found to consist of two almost disconnected parts which are proposed to originate from seniority-three proton and neutron cascades. Two isometric states are observed. A $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 45 ± 2}\text{ns}$ state at 1090 keV is proposed to have the main configuration and J^π = 10^?. A high-spin isomer with $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 1.5 ± 0.2 μs at 2276}\text{keV}$ is assigned to be the state. Shell-model arguments are used to assign configurations to most of the observed levels. Transition rates are discussed.     

Lifetimes and g-factors of the 6− and 7− isomers in 66Ga and 68Ga

The 6^? and 7^? isomeric states in ⁶⁶Ga and ⁶⁸Ga at 1440.9 and 1229.6 keV, respectively, have been populated with the (¹³C, 2np) and (¹⁵N, n2p) reactions on natural Fe. The half-lives of these states have been measured to be $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(6}{}^{\mathrm{?}}\text{,}{}^{66}\text{Ga}\text{) = 57.3 ± 1.2}\text{ns}$ and $\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{(7}{}^{\mathrm{?}}\text{,}{}^{68}\text{Ga}\text{) = 64 ± 2}\text{ns}$. Using previous data on the hyperfine field of Ga in Fe, the g-factors of these states have been determined by means of the TDPAD method. The results are $\text{g(6}{}^{\mathrm{?}}\text{,}{}^{66}\text{Ga}\text{) = 0.129 ± 0.003}$ and $\text{g(7}{}^{\mathrm{?}}\text{,}{}^{68}\text{Ga}\text{) = 0.105 ± 0.003}$. These values are in very good agreement with the independent particle model if one assumes the and configurations and uses the empirical proton and neutron g-factors from odd-A neighboring nuclei instead of the Schmidt values. The large disagreements with experiment when Schmidt values are used show that core polarization effects are important in these nuclei.     

Reorientational motion of the OH− ion in cubic sodium hydroxide

The rotational motion of the OH^? ion was studied in cubic NaOH at 575 K with quasielastic incoherent neutron scattering. The data are compared to two simple models yielding values for the radius of rotation R, the translational mean square displacement 〈u²〉_H, the rotational jump rate τ^?1 and the rotational diffusion coefficient D_R. The following parameter values are obtained: (a) rotational jump model: $\text{R = 0.95}\text{A}\text{?}$, $\text{〈u}{}^2\text{〉}{}_{\mathrm{H}}\text{= 0.052}\text{A}\text{?}{}^2\text{, τ}{}^{\mathrm{?1}}\text{= 2}\text{meV}$, (b) rotational diffusion model: $\text{R = 0.99}\text{A}\text{?}\text{, 〈u}{}^2\text{〉}{}_{\mathrm{H}}\text{= 0.046}\text{A}\text{?}{}^2\text{, D}{}_{\mathrm{R}}\text{= 0.72}\text{meV}$.