Magnitude Of Local Field Research Articles

Flavin Charge Redistribution upon Optical Excitation Is Independent of Solvent Polarity

Flavin absorption spectra encode molecular details of the flavin's local environment through coupling of local electric fields with the chromophore's charge redistribution upon optical excitation. Translating experimentally measured field-tuned transition energies to local electric field magnitudes and directions across a wide range of field magnitudes requires that the charge redistribution be independent of the local field. We have measured the charge redistribution upon optical excitation of the derivatized flavin TPARF in the non-hydrogen-bonding, nonpolar solvent toluene, with and without a tridentate hydrogen-bonding ligand, DBAP, using electronic Stark spectroscopy. These measurements were interpreted using TD-DFT finite field and difference density calculations. In comparing our present results to previous Stark spectroscopic analyses of flavin in more polar solvents, we conclude that flavin charge redistribution upon optical excitation is independent of solvent polarity, indicating that dependence of flavin transition energies on local field magnitude is linear with local field magnitude.

Study of geometrical surface barrier in Bi2Sr2CaCu2Ox single crystal by scanning spin probe

The field distribution in the Bi2Sr2CaCu2Ox rectangular strip, placed into perpendicular magnetic field, was studied. The measurement of local field magnitude was made using the ESR microprobe moved over the sample surface. Our results confirm the existence of geometrical barrier for vortex motion, which is due to edge shielding current, even at high magnetic fields. Changing the temperature we were able to observe the crossover of the magnetic field profile from the dome shape, typical for geometrical barrier (T>30K), to the steep front penetration picture (T<25K) of the bulk pinning case.

Waveform and polarization of compressional Pc 5 waves at geosynchronous orbit

The statistical characteristics of compressional Pc 5 waves are studied using magnetic field data obtained by GOES 2 and 3 geosynchronous satellites during 2‐year period of August 1978 to August 1980. Depending on the second‐harmonic component in the compressional component of the magnetic field oscillation, the compressional Pc 5 waves are classified into the three types: the harmonic, transitional and normal types. It is found that the harmonic and transitional types have significant azimuthal perturbations and show right‐handed polarization with respect to the local magnetic field. The occurrence of these types is limited to the region close to the effective equator in local time sector of 1500 ∼ 1700 LT, associated with a depression in the local field magnitude during geomagnetically active periods. Most of the normal type have small amplitude in the azimuthal component. However, when the normal type (corresponding to compressional Pc 5 waves examined in previous works) has a large azimuthal perturbation, it shows the left‐handed polarization. We try to find factors relating results to the excitation mechanisms developed in the past few years. Especially, we focus on the polarization properties of transverse perturbation which may reflect the spatial inhomogeneity of the media through the finite amplitude effect. It is suggested that the polarization of the transverse perturbation of compressional Pc 5 waves arises from that of the Alfvén mode.

Stormtime Pc 5 magnetic pulsations observed at synchronous orbit and their correlation with the partial ring current

Stormtime Pc 5 pulsations are a class of magnetic pulsations observed at synchronous orbit most frequently during the main phase of magnetic storms. The waves are linearly polarized in a meridian plane with nearly equal compressional and transverse components. The waves usually accompany a depression in local field magnitude associated with the onset of a magnetospheric substorm. In this paper, we use local time‐universal time maps of mid‐latitude magnetic perturbations to study the association of these waves with the development of the partial ring current. We find that these waves occur at the local time of maximum development of the partial ring current, at or shortly after the onset of a magnetospheric substorm. These results confirm our earlier speculation based on satellite data alone that the waves are associated with substorm enhancement of the partial ring current.

Chlorine NQR in Antiferromagnetic PrCl3

Colwell and Mangum1 have observed a sharp peak in the specific heat of PrCl3 near 0.4°K which they interpreted as a transition to an AF state. We have observed the 35Cl nuclear quadrupole resonance line2 at 4.567 MHz to split below this temperature into two lines. The behavior in a small magnetic field is consistent with an Ising AF with the magnetic moment along the C3 direction, and implies a symmetry of P2c3̄ (antiferromagnetic chains). At the lowest temperature reached, 0.31°K, the splitting is 80 kHz. The projection of the local field at the Cl site on the xy plane of the principle axis system of the electrostatic field gradient is approximately along the bisection of y and z. The angle between the local field and x, C3, is approximately 30°. The magnitude of local field is about 500 G for a splitting of 80 kHz. Lineshape changes in the short range ordering region above TN are observed.