A generalization of the fluctuation-dissipation theorem for the case of excess noise

Electrical fluctuations proportional to the square of the external field are investigated in the case of quasi-equilibrium conditions. The binary correlation function, proportional to the square of the external field, is expressed in terms of the zero-field quaternary correlation function for both quantum and classical cases. This result can be considered as a generalization of the fluctuation-dissipation theorem. The 1/f spectrum is obtained as a consequence of the symmetry properties of the quaternary correlation function without consideration of the physical mechanisms responsible for the noise. The method of investigation of the 1/f spectrum through zero-field quaternary correlation function is discussed.     

Superparamagnetic-like behaviour of magnetic alloys

The effect of antiferromagnetic interaction on a binary Ising ferromagnetic alloy A_pB_1?p is studied based on cluster-variational method and assuming either J_AB or J_BB or both exchange interactions to be of antiferromagnetic type. In a ferromagnetic state the moment saturates to a value much lower than its full value. Within the temperature interval where moment saturates, the system exhibits superparamagnetic-like behaviour. The induced moment becomes a function of $\text{h}\text{T}$ only, and the zero-field susceptibility follows Curie law. The incomplete saturation of moment persists up to a large value of $\text{h}\text{T}$. The short-range order parameter at T = 0 is much less than that of homogeneous ferromagnet.     

Mobility of CO on the (110) plane of Tungsten

The measurement of time autocorrelation functions of field emission current fluctuations has been applied to the adsorption of CO on the (110) plane of tungsten. For molecularly adsorbed virgin-CO, no evidence for diffusion was found at any coverage, although a weak, exponentially decaying correlation function, suggesting flip-flop between differing ad-sites, was seen. A hysteresis in the mean square fluctuation could be clearly identified with conversion to β-CO. For the latter state a flip-flop signal was seen for 280 ? T ? 650 K, and for T$\text{\$}\text{?}$650 K a correlation function corresponding to diffusion was found. The activation energy of diffusion was 23 kcal, independent of coverage. This value agrees closely with that found for oxygen diffusion at $\text{O}\text{W}$ = 0.5. For CO readsorbed on a β-layer (α-CO) neither diffusion nor flip-flop was seen.     

Susceptibility divergence of the spin 1 Ising model on the Cayley tree

The temperature T₂(1), below which the zero-field isothermal susceptibility diverges for the spin 1 Ising model on the M-generation Cayley tree, in the limit as M → ∞, is located. The general approach follows closely that of Falk for the spin $\text{1}\text{2}$ problem. Pruning and retraction identities are used to find upper and lower bounds on the bond-length dependence of the general two-spin correlation function and thence on the susceptibility. A conjecture is advanced regarding the divergence of the higher-order susceptibilities.     

The assignment of molecular infrared spectra from a laser magnetic resonance spectrometer

Mathematical techniques are presented which have proved useful in assigning the laser magnetic resonance pure-rotation spectrum of HO₂, i.e., useful in assigning an absorption spectrum obtained when molecular energy levels are Zeeman shifted by an external magnetic field until transition frequencies coincide with a fixed-frequency radiation source. The techniques described should have general applicability to the laser magnetic resonance vibration-rotation spectrum of any molecule in an orbitally nondegenerate electronic state and a doublet electronic spin state ($\text{S =}\text{1}\text{2}$). Equations involving both Zeeman line positions and Zeeman line intensities are presented. These allow the assignment of M_J quantum numbers, the determination of the spin-rotation interaction constant γ and rotational quantum number N for both the upper and the lower state, and the determination of the zero-field transition frequency. The equations can be used without prior knowledge of the molecular structure or energy levels.     

The role of magnetic clusters in mictomagnetic alloys

The average moment and the concentration of magnetic clusters in $\text{Cu}$-Mn alloys were determined from magnetization data. Both are increased by aging. Magnetic clusters are responsible for most of both the extremely large steady field susceptibility at 4.2°K after zero-field cooling and the alternating low-field susceptability at its peak.     

Geminate and non-geminate recombination in a-As2Se3

Combined zerographic measurements and a delayed-collection field technique has been applied to a-As₂Se₃. The data shows that the zero-field quantum efficiency is 0.45±0.02. The measured field and temperature dependence gives a best fit to the Onsager theory with $\text{r}{}_0\text{=80}\text{A}\text{?}$ for Φ₀=1. Non-geminate recombination was studied using a delayed-collection field technique as a function of the time delay of the collection field. The results indicate a remarkably long recombination lifetime≈1 sec at room temperature which is diffusion-controlled.     

On the calculation of dielectric properties from computer simulations

We report a reaction field calculation for Stockmayer particles at reduced density $\text{?}{}^1\text{= 0.8}$, reduced temperature $\text{T}{}^1\text{= 1.35}$ and reduced dipole moment $\text{μ}{}^1\text{= 1.64}$ using a relatively large cutoff distance for the dipolar interaction. The dipole-dipole correlation function is compared with corresponding simulations using truly periodic boundary conditions. The mean square fluctuation of the total dipole moment are shown to exhibit a long period oscillation, precluding a determination of the dielectric constant with an accuracy better than 15%, in a Monte-Carlo calculation of the order of 5 × 10⁶ configurations.     

Theory of the liquid-solid transition

The liquid-solid transition is found by calculating the thermodynamic potential of a dense classical system as a function of order parameters which are proportional to the lattice Fourier components of the density. Properties of the fluid enter $\text{only}$ through the direct two-particle correlation function near freezing. Calculated parameters for freezing into bcc, fcc and hexagonal structures are in good agreement with experimental results.     

Nuclear magnetic resonance of extremely dilute CrFe

We report nuclear orientation and pulsed NMR on radioactive ⁵¹Cr$\text{Fe}$ samples. The zero-field resonance frequency of 13.543(18) MHz from polycrystalline foil samples yields a hyperfine field B_hf = ?6.655(35) T in the dilute, low-temperature limit for Cr$\text{Fe}$.     

Intersections of quasi-energy levels in the relativistic theory of multiply charged ions

The relativistic generalization of the quasi-energy method is given with the help of which the influence of an alternating electric field on the energy levels (2 $\text{1}\text{2}$ 0), (2 $\text{1}\text{2}$ 1) of multiply charged H-like ions is investigated. Intersections are found of quasi-energy levels in external fields with frequencies ω₀ ? ΔE_L and definite values of the field amplitude.     

High-frequency Franz-Keldysh effect on excitons

When the effective characteristic electro-optic energy ?|Λ_H|, which is obtained by including the electron-hole interaction in the solid, is very large compared to ?ω of the modulating electric field, the line shapes of the field-induced change of dielectric function are the same as those of Franz-Keldysh effect. However, in the low-field and high-frequency limit Δ∈₂(Ω, $\text{E}$ is nearly proportional to the first derivative of the unperturbed dielectric function. It is different from the low-field and low-frequency limit case where Δ∈₂(Ω, $\text{E}$) is proportional to the third derivative of the unperturbed dielectric function.     

The magnetic moment of the first excited state of 19O

The magnetic moment of the first excited 96 keV, $\text{3}\text{2}{}^{\mathrm{+}}$ state of ¹⁹O has been determined by an integral perturbed angular correlation measurement in a transverse external magnetic field. The value obtained for the g-factor, ?0.48(6), is discussed in terms of shell-model configurations. The wave function of the $\text{3}\text{2}{}^{\mathrm{+}}$ level is shown to consist mainly of the $\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}{}^3$ configuration.     

Critical scaling function for long-range interactions to order 1/n

A universal scaling function of the order-parameter correlation function for an n-vector system in d dimensions, with long-range interactions $\text{～1/z.sfnc}\text{r}\text{z.sfnc}{}^{\mathrm{d+\sigma }}$, is discussed on the basis of explicit zero-field calculations to order 1/n, for T?T_c and σ<d<2σ.     

Excited states of six-membered aza-aromatic rings. IX. 1,4- and 5,12-diazatriphenylenes

The two isomeric diazatriphenylenes, 1,4-DAT and 5,12-DAT, and the corresponding singly and doubly protonated forms were investigated in the ground state, phosphorescent state and fluorescent state by the methods of electronic spectroscopy, ESR spectroscopy and quantum chemistry. The following properties were measured: (π, π¹) excitation energies, acid-base equilibrium constants, quantum yields of fluorescence, lifetimes and zero-field splitting parameters of the triplet states, for the bases and the conjugate acids. The results of semi-empirical calculations performed using the PPL LCI SCF method based on monoexcited configurations were compared with experimental data. The calculated electron densities on nitrogen were correlated with pK's for the two equilibria and the three electronic states. The unusually large increase of pK (by about six units) of the triplet 1,4-DAT, has been found and interpreted. A very good correlation of zero-field splitting parameter D^{$\text{1}\text{3}$} versus singlet-triplet splitting was obtained.     

Solving the linearized Φ4 equation in external driving fields

The Φ⁴ equation, linearized about a kink at rest, is solved for external driving fields F(t) = Σ_i=n^∞f_itⁱ. The x-dependent part of the solution $\text{u}\text{?}\text{(x, t)}$ is proportional to the translation mode. This implies that also for large times the kink's dynamics is adiabatic, if the external field is sufficiently weak and $\text{|}\text{u}\text{?}\text{|? z1}$|ν| ? 1.     

Measurement of the magnetic moment of the first excited state of 15C

The g-factor of the $\text{5}\text{2}{}^{\mathrm{+}}$ first excited state of ¹ has been measured in a time integral, external magnetic field, perturbed angular correlation experiment. A value of g=?0.77 ± 0.06 was obtained. In addition, the energy of the state was accurately measured to be 739 ± 1 keV.     

Magnetic field dependence of the nuclear spin—lattice relaxation of 93mMo and 94,95Tc in Fe

The nuclear spin—lattice relaxations of ^93mMo$\text{Fe}$ and ^{94, 95}Tc$\text{Fe}$ at T ? 10 mK have been investigated with frequency- modulation-pulsedNMR on oriented nuclei as a function of an external magnetic field B₀. In the range 0?B₀?6kG the relaxation constant varies by a factor >10 and ?6 for ^93mMo$\text{Fe}$ and ^94,95Tc$\text{Fe}$, respectively. The high-field Korringa constants for ^93mMo, ⁹⁴Tc and ⁹⁵Tc in Fe were determined to be 2.5(4), 1.3(4) and 0.55(10) sK.     

Variation of the local field through the liquid-vapour interface

We derive an integral equation for the self-consistent local field E^loc(z) within an inhomogeneous non-polar fluid, with particular application to the liquid-vapour interface. Approximate solutions are given for the cases of induced atomic dipoles oriented perpendicular and parallel to the interface. For the perpendicular case we relate the average field to the local field and thus obtain an equation for the static dielectric constant ?(z) in terms of the density profile n(z). The departures of the local field from Lorentz form $\text{E}{}^{\mathrm{<mtext>ext</mtext>}}\text{/(1 + (}\text{8}\text{3}\text{)παn(z))}$ and of the dielectric constant from the Clausius-Mossotti form ($\text{1 + (}\text{8}\text{3}\text{)πan(z))/(1 ? (}\text{4}\text{3}\text{)παn(z))}$ are shown to be small. For the parallel case we discuss fringing of the external field and show that the dipoles align themselves with the average field, not the external field. The departure of the local field from $\text{E}{}^{\mathrm{<mtext>ave</mtext>}}\text{/(1 ? (}\text{4}\text{3}\text{παn(z))}$ is shown to be small.     

General form of the local magnetization in the XY chain with impurity

Green's function technique in the pseudofermion representation is used to study the oscillation of the local magnetization in the impure spin $\text{1}\text{2}$XY chain. The theory described in the previous work is extended to the case when both the exchange integral in the immediate vicinity of the impurity and its g-factor are different from the bulk of the chain. The results are obtained in the closed form and are interpreted in terms of the local density of states. It is shown that Friedel-type oscillations of the spin density, resulting from the different components of the perturbation, have phase shifts depending on the intensity of the external magnetic field.