Photoabsorption spectra of boron nitride fullerenelike structures

Optical absorption spectra have been calculated for a series of boron nitride fullerenelike cage structures BnNn of sizes n=12-36. The method used is a real-time, real-space implementation of the time-dependent density-functional theory, involving the full time propagation of the time-dependent Kohn-Sham equations. The spectra are found to be a possible tool for distinguishing between different boron nitride fullerene species and isomers. The trends and differences in the spectra are found to be related to the general geometry of the molecules. Comparison between local-density and generalized-gradient approximations for electron exchange-correlation functionals shows that both of them produce essentially the same spectral characteristics.     

Laser spectroscopy at IGISOL IV

The IGISOL (Ion Guide Isotope Separator On-Line) facility at the University of Jyväskylä accelerator laboratory has been upgraded and relocated to a purpose built laboratory. The new laboratory includes a dedicated MCC30 proton/deuteron cyclotron, which in conjunction with beams from the K130 cyclotron, will greatly increase the beam time available at the facility. Full off-line commissioning of the laser spectroscopy beam-line was achieved in February 2013 and on-line commissioning with radioactive beams was achieved in May 2013. Optical hyperfine resonance spectra were obtained for previously studied radioactive molybdenum isotopes and used to investigate our long term stability, efficiency and ability to successfully reproduce previous results from IGISOL III. A preliminary spectrum for the previously unmeasurable $^{107}$ Mo was collected, displaying the improved capabilities of the new facility. Both data-sets show that the laser-line is ready for future experiments. The IGISOL IV beams are cleaner and have a higher radioactive content compared to similar experiments at IGISOL III.     

Entropy of formulas

A probability distribution can be given to the set of isomorphism classes of models with universe {1, ..., n} of a sentence in first-order logic. We study the entropy of this distribution and derive a result from the 0–1 law for first-order sentences.