The elastic behaviour of In-Tl alloys in the vicinity of the martensitic transition

To test further the prediction of collapse of the [110], q|| [11̄0] acoustic mode at the martensitic phase transition, pulse superposition measurements of ultrasonic wave velocities have been made in indium-thallium alloys containing 25 and 27 at. % thallium. These alloys are f.c.c. at room temperature and transform on cooling to the f.c.t. phase at 196 ± 2°K and 127 ± 2°K, respectively. Results show that $\text{1}\text{2}$(C₁₁ ? C₁₂) goes to zero within experimental error at the transition temperature. The room temperature elastic constants of the tetragonal 11.5 and 15 at. % thallium alloys are also reported.     

Intensity and half-width measurements in the 1·525 μm band of acetylene

Line intensities at 150°K and 295°K, self-broadened half-widths at 171°K, 200°K, 250°K and 295°K, and hydrogen-broadened half-widths at 171°K, 200°K and 295°K have been measured in the ν₁+v₃ band of C₂H₂ at 1·525 μm. The absolute intensity of the band has been determined independently by employing the Wilson-Wells-Penner-Weber technique. Our best estimate for the absolute intensity of the band is S_v=7·82 ± 0·07 cm^?2 atm^?1 at 295°K. Line intensities calculated using this value of S_v are in good agreement with the measured intensities at the two extreme temperatures of 150°K and 295°K considered in the present study, thereby not suggesting any significant intensity anomalies. Line positions have been measured for the first time for this band for R(29)?P(25).     

Measurement of intensities of multiplets in the 2ν3-band of methane at low temperatures

The integrated intensities of the multiplets P(1)–P(10), R(0)–R(9), and of the Q-branch in the 2ν₃-band of ¹²CH₄ have been measured at 102°K, 152°K, 202°K, 251°K, and 300°K. Comparison of our data with theoretical line strengths confirms, at all of the temperatures mentioned, the intensity anomalies observed by Margolis⁽⁵⁾ for lines in this band. The integrated intensity of the 2ν₃-band is found to be S_v = (1·76±-0·04)(300/T (°K)) cm^?2 atm^?1.     

Measurements of intensities and nitrogen-broadened linewidths in the CO fundamental at low temperatures

Intensities and nitrogen-broadened half-widths of lines R(0), R(8) and R(16) in the fundamental band of ¹²C¹⁶O have been measured at 83°K, 100°K, 150°K, 200°K and 298°K. The intensities of several other lines in the P- and R-branches of the band have also been measured at 298°K. The absolute intensity derived from the line intensity data using the Herman-Wallis formula is S^°_v = 273 ± 10 cm^-2atm^-1 at S.T.P. A separate measurement employing the Wilson-Wells-Penner-Weber method has yielded S^°_v = 277 ± 4 cm^-2 atm^-1 at S.T.P. Both of these values are within 6 per cent of most of the previously published direct measurements of this parameter. The values for the line intensities reported earlier by other authors are lower by nearly 16 per cent.     

Oscillator strengths from line absorption in a high-temperature furnace—II. The (0,0) band of the B2σ+—X2σ+ transition in CN*

Quantitative high-resolution absorption spectroscopy was applied to the (0,0) violet band of CN. The CN radical was prepared in a furnace at 1421°K containing pure cyanogen gas. Since the calculated CN concentration is dependent on the controversial CN heat of formation, only the relationship, f_υ = 6·84 X 10^-3exp (0·354δ), where f_υ is the excess over the initially assumed ΔH⁰_f(CN) = 100·8 kcal/mole, could be directly determined in this study with an estimated error in f_υ of ±20%. For δ = 0, our f_υ is a factor of 4·8 smaller than an average value of 0·033±0· derived from other measurements. If this latter value of f_υ is assumed, our relationship yields ΔH⁰_f(CN) = 105·3±1· kcal/mole or D₀(CN) = 7·66±0·05 eV. The rotational temperature and line widths for this band were also measured.     

Mößbauereffekt in Eisenstilben und FeCl2·H2O

Using Mößbauer effect measurements in the temperature range between 3 °K and 310 °K the magnetic fields at the nucleus in iron-stilbene, FeCl₂·H₂O and FeCl₃ are determined to beH _T=0=(250±10) kOe, (252±18) kOe and (468±10) kOe; a Néel-temperature ofT _N=(23±1) °K is measured for iron-stilbene. The electric quadrupole splittings atT=0 °K for iron-stilbene and FeCl₂ ·H ₂ O, ΔE=(+2.52±0.02) mm/sec and (+2.50±0.05) mm/sec, yield electric field gradients at the iron nucleus ofq _z=+9.7·10¹⁷ V/cm² and +9.6·10¹⁷ V/cm², whereq _z⊥H; Debyetemperatures of θ=162 °K and 188 °K are obtained. The energy of the excited 3d-electron levels in iron-stilbene is estimated to Δ₁=309 cm^?1 and Δ₂=618cm^?1 as deduced from the temperature dependence ofΔE. In contrast to the suggestion ofEuler andWillstaedt bivalence of the iron in ironstilbene is found; its composition is shown to be 4(FeCl₂ ·H ₂O)·stilbene.     

Spectroscopic diagnostics of R.F. discharges at moderate pressure and chemical applications—I. Pure nitrogen

A vibro-rotational analysis has been performed of the second positive system (SPS) of N₂ and of the first negative system (FNS) of N⁺₂ emitted by 35 MHz discharges in flowing nitrogen operated at pressures of 5–50 torr and power densities of the order of 1–10 W-cm^-3. The distributions of the vibrational and of the rotational levels follow Boltzmann's law in both the SPS and the FNS with T_v = 4000°K and T_R = 2800°K for the N₂(C³Π_u) state and T_v = 5100°K and T_R = 5800°K for the N⁺₂(B²Σ⁺_g) state and independent of pressure. Kinetic gas temperatures are between 1200 and 2000°K and increase with pressure; electron temperatures are in the range 15,000–9,500°K. The reversal of line intensities of the SPS and of the FNS observed with increasing pressure has been tentatively interpreted. Possible chemical implications of these results have been examined.     

Analytical properties of the forward elastic scattering amplitudes following from microcausality

The forward elastic scattering amplitudes T_i(v,q²), (i = 1,2), of the virtual photon with the mass q² are considered in variables σ and ? where σ and ? are related to q² and v by the formulae q² = exp (2σ) and v = exp (σ) ch?. It has been proved that microcausality requirement implies the analyticity of amplitudes in the tube region [Im σ + π/2] + |Im?| < π/2 as a function of both complex variables σ and ?. Formulae are obtained expressing amplitudes T_l(v,q²) at arbitrary v and q² through functions W_l^(?)(v, q²) describing the electroproduction process ?2v < q² < 0.     

Low temperature elastic constants and Debye temperature of NbO2

The transit times of ultrasonic waves have been measured in single crystal NbO₂ from 295 K down to 1.5 K for quasilongitudinal and shear waves propagating in the [100] direction and down to 160 K for eight other waves. Values are obtained for the C₄₄ elastic constant and for an elastic constant combination which is approximately equal to C₁₁ for temperatures down to 1.5 K and for C₁₁, C₁₂, C₁₃, C₁₆, C₃₃, and C₆₆ down to 160 K. These results are used to deduce 0 K values for the elastic constants and an elastic Debye temperature of 596 ± 7 K at 1.5 K. The acoustic mode heat capacity calculated from the latter is significantly smaller than the heat capacity measured by Wenger and Keesom at low temperatures. Following Wenger and Keesom, the difference is attributed to phasons (excitations involving the phase modulation of charge density waves). An average velocity is deduced for the phasons.     

Quantum integrable systems related to lie algebras

Some quantum integrable finite-dimensional systems related to Lie algebras are considered. This review continues the previous review of the same authors [83] devoted to the classical aspects of these systems. The dynamics of some of these systems is closely related to free motion in symmetric spaces. Using this connection with the theory of symmetric spaces some results such as the forms of spectra, wave functions, S-matrices, quantum integrals of motion are derived. In specific cases the considered systems describe the one-dimensional n-body systems interacting pairwise via potentials g²v(q) of the following 5 types: v_I(q) = q^?2, v_II(q) = sinh^?2q, v_III(q) = sin^?2q, $\text{v}{}_{\mathrm{<mtext>IV</mtext>}}\text{(q) =}\text{P}\text{(q)}$, v_V(q) = q^?2 + ω²q². Here $\text{P}\text{(q)}$ is the Weierstrass function, so that the first three cases are merely subcases of the fourth. The system characterized by the Toda nearest-neighbour potential exp(q_jq_{j+ 1}) is moreover considered.This review presents from a general and universal point of view results obtained mainly over the past fifteen years. Besides, it contains some new results both of physical and mathematical interest.     

Giant quantum oscillations of the magnetothermoelectric coefficient in semimetallic Sb-Bi and Sb-As alloys

Quantum oscillations of the magnetothermoelectric coefficient α_ii(B) are investigated in semimetallic Sb-Bi and Sb-As alloys in stationary magnetic fields up to 15 T and at temperatures from 1.9 to 30 K. Quantum oscillations of α_ii(B) of a giant amplitude are observed when the longitudinal or transverse magnetic field is oriented along a binary C ₂ axis or a bisectory C ₁ axis and also when rotating the transverse magnetic field in angle ranges up to [+55°, ?55°] around them.     

Electric-quadrupole interaction at 181Ta in f.c.t. ZrHi1.97

Time-differential perturbed γ-ray angular correlation experiments have been carried out on ¹⁸¹Ta impurities in ?-phase zirconium hydride over the temperature range from 20 to 588 K. A static, slightly asymmetric electric quadripole interaction is found at all temperatures. The static nature of the pattern indicates the absence of significant hydrogen diffusion at these temperatures on the time scale of the experiment (0.1 μsec). The temperature dependence of the static quadrupole frequency is given by the relation v_q(t) = 130[1 ? (1.9 × 10^?5)T^1.5] MHz.     

Sound velocity in single crystals of synthetic opals

The [111] longitudinal sound velocity (v _L) in a single-crystal synthetic opal has been measured at a frequency of 10 MHz in the temperature range 4.2–300 K. At 300 K, v _L=2.1×10⁵ cm/s. The quantity dv _L/v _{300 K}(T) (where v _T,K?v_{300 K}) in the ranges 4.2–200 and 200–300 K behaves in the way typical of amorphous and crystalline solids, respectively.     

Elastic constants of solid krypton at T = 77 K determined by inelastic neutron scattering

Long-wavelength acoustic phonons have been studied for each of the [ζ00]T, [ζ00]L, [ζζ0]L and [ζζ0]T₁ branches in solid Kr at T = 77 K by means of inelastic neutron scattering utilizing ‘cold neutrons’ as they are available in the long-wave length tail of the pile spectrum. The raw data have been corrected for resolution effects taking into account the curvature of the dispersion surface and variation of mode eigenvectors. It has turned out, that this yields appreciable shifts of the raw data. The results of our experiment give c₁₁ = 4·25 ± 0·10, c₄₄ = 2·04 ± 0·03, c₁₂ = 2·82 ± 0·12 and a value for B = (c₁₁ + 2c₁₂)/3 = 3·30 ± 0·09 × 10¹⁰ dyne/cm². Available thermodynamic data for Kr gives a derived value for B^ad = 2·58 ± 0·06 × 10¹⁰ dyne/cm² indicating a large difference between zero sound and first sound in solid Kr at high temperatures.     

Measurement of hydrogen- and self-broadened half-widths of ammonia at 200 and 300°K

The hydrogen- and self-broadened half-widths have been measured for the (v₁+v₂)- and (v₂+v₃)-bands of ammonia at 300 and 207°K. Measurement of hydrogen-broadened widths has been restricted to J, K ?6, but that of self-broadened widths is done for a few lines outside that range. Assuming a power-law dependence of half-width on temperature given by γ(T)=γ(T₀)(T/T₀)^α, the average value of the index α for the lines measured is found to be 0·57 for hydrogen broadening.     

Orientation of adsorbed ethylene oxide on Ni(110) by X-ray photoelectron diffraction

The adsorption of ethylene oxide on Ni(110) was studied at 95 K and monolayer coverage by angle-resolved X-ray photoelectron spectroscopy. A slow radiation-induced decomposition at hv = 1486.7 eV to most likely methoxy was noted. The orientation of the adsorbed ethylene oxide was determined by measuring forward scattering enhancements in the O 1s intensity distribution. Peaks in polar (θ) as well as azimuthal (φ) scans occurred at four angular positions in 2π above the surface: (θ = 54°, φ = 36°, 144°, 216°, 324°). These positions were evaluated to yield the tilt angle of the molecule at 48°_relative to normal, and the COC bond angle of adsorbed C₂H₄O of about 57°. The molecule is tilted towards the [001] and [001&#x0304;] directions (two domains), with a mirror plane in the [001] azimuth.     

Intensity measurements in the 2v3-band of 13CH4 at low temperatures

Absolute intensities of the J-multiplets P(1)-P(8), R(0)-R(7) and of the Q-branch in the 2v₃-band of ¹³CH₄ have been measured at 100, 150, 200, and 296°K. Our intensity data confirm the recent observation by Fox et al. that substitution of the isotope ¹³C for the central ¹²C atom in methane results in significantly different line strengths in the severely perturbed 2v₃-band. Our results at 296°K for the absolute intensities of R(0) and R(1) are in excellent agreement with the values measured by Fox et al.     

Zur Chronologie des alten Ägypten

The velocityv of the propagation of discharge along the anode of a self-quenchingG—M-counter is a function of total pressureP, pressure of the quenching gasP _D, radius of the cathoder _a and of the anoder _i andV _ü the difference between working- and starting-potential. For the mixtures argon-methylal, argon-alcohol and helium-alcohol isv=v ₀·exp[k·(V _ü/V _e)^1/2] withv ₀ the velocity at the starting potentialV _e v ₀=(a+b·P _D/P)·V _n ^1/2 ·exp [(c?d·P_D/P·V _n ^?1/2 ] andV _n=V _e·(lnr _a/r _i)^?1.k, a, b, c andd are characteristical constants of the filling gas.     

High resolution measurements of the line positions and strengths of the 2ν2 band of H2CO

Spectra of the 2ν₂ band of formaldehyde have been obtained with high resolution (0.035 cm^?1). Measurements were made with path lengths of 8, 16, and 24 m and at sample pressures from 0.1 to 0.3 mm Hg at room temperature (～296°K). From these data, the following constants were determined for the 2ν₂ band in wavenumber units: v₀=3471.718±0.004,A=9.3958±030013,B=1.28100±0.00024,C=1.11662±0.00024, Tbbb=-12.8±0.5×10^-6,Taabb=60±5×10^-6. The line strengths were also obtained from the data. The strengths were analyzed to determine the band strength and the rotational factors. At 296°K, the strength of the 2ν₂ band was found to be 15.5 ± 0.9 cm^?1/(cm·atm).     

Ferromagnetic ordering in the MMnF6 series (M = Ni,Cu, Zn,Pd)

Neutron diffraction experiments performed on MMnF₆ compounds (M = Ni, Cu, Zn, Pd) have shown that both NiMnF₆ and ZnMnF₆ crystallize in the rhombohedral R$\text{3}$ space group with a cationic ordering, whereas PdMnF₆ shows cationic disordering (R$\text{3}$c, a = 5.46 Å, α = 54.45°). CuMnF₆ has a monoclinic distortion derived from the MnF₃ structural type (a = 8.57 Å, b = 4.85 Å, c = 13.46 Å, β = 92.12°). The magnetic properties can be correlated with the structure: the R$\text{3}$ ordered compounds show a ferromagnetic behavior (T_C(NiMnF₆) = 39 K; T_C(ZnMnF₆) = 9.5 K; T_C(CdMnF₆) = 8 K), while the other two have an antiferromagnetic ordering.