Demonstration of a transient-gain nickel-like xenon-ion x-ray laser

We demonstrate a high-gain nickel-like xenon-ion x-ray laser, using a picosecond-laser-irradiated gas-puff target. The elongated x-ray laser plasma column was produced by irradiation of the gas-puff target with line-focused double picosecond laser pulses with a total energy of 18 J in a traveling-wave excitation scheme. Strong lasing at 9.98 nm was observed, and a high gain coefficient of 17.4 cm(-1) was measured on the transient collisionally excited 4d-4p , J=0-1 transition for nickel-like xenon ions with target lengths as great as 0.45 cm. A weak nickel-like lasing line at a shorter wavelength of 9.64 nm was also observed, with a gain coefficient of 5.9 cm(-1) .     

Nitrogen inversion in 3,6-dihydro-1,2-oxazines

The nitrogen inversion barriers of nine 3,6-dihydro-1,2-oxazines are discussed. Polar solvents were found to increase the nitrogen inversion barriers which, in turn, decrease with increasing size of the N-substituent.     

Metal-Enhanced Fluorescence Solution-Based Sensing Platform

In recent years our laboratories have reported the favorable effects for fluorophores placed in close proximity to surface immobilized silver nanostructures. These include; greater quantum yields, reduced lifetimes (increased photostability) and directional emission. However, while these findings are likely to find multifarious applications for surface assays based on enhanced fluorescence detection, a solution based enhanced sensing platform has yet to be realized. In this short, note, we show how SiO2-coated silver colloids, indeed provide for a solution based enhanced fluorescence sensing platform with a 3-5 fold enhancement typically observed.     

Author Index for Volume 12

Authors Index

Author Index for Volume 12     

Theoretical model for the double fluorescence of p-cyano-N,N-dimethylaniline in polar solvents

The energies of the low lying electronic states of p-cyano-N,N-dimethylaniline (CDMA) in its planar and in 90° twisted conformation have been calculated using the modified INDO method. Solvent effects have been taken into account. The results agree reasonably well with the experimental data and support the hypothesis of the dual fluorescence of CDMA as being related to the intramolecular rotation of the N(CH₃)₂ group, with a decisive role of the solvent polarity.     

Charge transfer theory and vibrational properties of the hydrogen bond

An extension of Mulliken's charge transfer theory leads to the following correlations: the change in the transition moment of the X—H stretching vibration with the enhancement of dipole moment, and the displacement of the X—H stretching frequency with the ionization of donors. Experimental data for a number of hydrogen-bonded complexes are in accord with these predictions.