Intensity and polarization of laser-induced fluorescence due to forbidden excitation of He atoms immersed in an electric field in plasmas.

Laser-induced fluorescence (LIF) processes through the Stark and electric-quadrupole moment (QDP) transitions of HeI (2(1)S-->n1D-->2(1)P,n=3,4) have been investigated for reliable electric-field measurements in plasmas. A linear-polarization model is formulated for various configurations of electric fields, magnetic fields, and laser polarization. To extend the model to higher-particle-density plasmas we develop a rate-equation model involving a collisional disalignment term. Disalignment rates of n1D states, Rda, due to a collision with He gas were measured. Spatial distributions in intensity and polarization of LIF were observed in a discharge plasma. For n=3 with small Rda, the same electric-field distribution in the sheath was obtained from either of the intensity ratios of the Stark to QDP component and the polarization, and the sheath potential agreed well with that by an electric probe. For n=4 with large Rda, the distribution was also correctly obtained from partially depolarized LIF wave forms by using the extended model. These results show that our extended model provides an accurate measurement of the electric field. The minimum detectable field strength was 80 V/cm for n=4. Application and limitations of the methods are discussed.

Enhancement of double auger decay probability in xenon clusters irradiated with a soft-x-ray laser pulse.

The interaction of large Xe clusters with a soft x-ray laser pulse having a wavelength of 13.9 nm and an intensity of up to 2x10(10) W/cm2 was investigated using a time-of-flight ion mass spectrometer. The corresponding laser photon energy was sufficiently high to photoionize Xe 4d innershell electrons. It was found that Xe3+ ions (which result from double Auger decay of 4d vacancies) became the dominant final ionic product with increasing cluster size and x-ray intensity. This is in contrast to the results of synchrotron radiation experiments involving free Xe atoms, in which Xe2+ is the dominant resultant ion species. Possible mechanisms responsible for the enhancement of the double Auger transition probability in x-ray laser and cluster interaction are discussed.

Influences of protein malnutrition on amino acid composition, trace metal elements and tensile strength of rat hairs.

We examined hair properties from determinations of diameter, amino acid composition, trace metal elements, and tensile strength of the hairs from protein-malnourished rats. The coarse or medium hair diameters of the experimental protein-malnourished rats had a tendency to decrease more than those of the control. Total contents of amino acids in the hairs had a tendency to decrease in the protein-deficient rats. Cystine content of rat hairs definitely decreased only in 5% wheat- and 5% rice-pattern amino acid mixture diet groups but not in 5% gluten diet and 5% casein diet groups. And many of the low-protein diet groups were significantly lower in methionine content than the control except for the 5% casein diet group. The Mg, Zn, and Fe contents in the hairs considerably increased in protein-deficient rats against the control. Tensile strength of coarse hairs in the experimental protein-malnourished rats was significantly lower than that of the control. The changes in amino acid composition of rat hair proteins are more likely to be influenced by various qualities of dietary protein or different compositions of amino acid mixtures in the diets at a similar dietary protein level. It should seriously be considered from our data whether the reduced cystine content in the hair can be regarded as an indicator of nutritional status.

Eigenvalues of a nonconfocal laser resonator with an output-coupling aperture.

A nonconfocal laser resonator that has output-coupling apertures has been analyzed using the matrix eigenvalue technique. Numerical calculations of eigenvalues and eigenfunctions are performed for the interesting resonator consisting of one plane mirror with a coupling aperture and one spherical mirror. The effects of the coupling aperture are also discussed for several kinds of modes when both the mirror and coupling- aperture Fresnel numbers vary. It is found that the power loss of the TEM(00) mode becomes nearly constant in a finite range of the mirror Fresnel number. In such a range, the major source of a resonator loss is the power coupling through an aperture, and the coupling loss can be estimated independently of the loss caused by the spillover at mirror edges.