Coupled channel analysis of inner-shell vacancy formation in superheavy quasimolecules

We calculate the ionization probability of the quasimolecular 1sσ-state in collisions of very heavy ions with (Z ₁+Z ₂) α?1. Multistep excitation processes between bound and continuum states are investigated. Due to the multistep processes the number of created 1sσ-vacancies is typically increased by a factor 2–5 over that obtained within time-dependent perturbation theory (i.e. the one-step processes). Some implications of the many-electron problem and the Pauli principle are discussed. The δ-electron distribution is compared with recent experimental data.     

Basic investigations on background problems in the platinum-loop method in comparison to graphite-furnace and flame atomic-absorption spectrophotometry

The platinum-loop method of flame-AAS/AES gives lower detection limits for volatile elements than conventional working modes of flame-AAS/AES. The background problems of the method are compared with those of the other AAS-techniques (flame- and furnace-AAS). In this initial study, the background spectra of two alkali-metal halides (NaCl, NaI) are investigated. It is found that for NaCl the intensity of the molecular background absorption is about 400 times greater in the furnace method than with the loop technique. In the short wavelength region of the spectrum (<220nm) Raleigh scattering is negligible in the loop method, compared with furnace-AAS.     

Two remarkable doubly exponential series transformations of Ramanujan

The purpose of this note is to prove two doubly exponential series transformations found in Ramanujan’s second notebook. Dedicated to the memory of Professor K G Ramanathan     

Picosecond fluorescence lifetime detector

A gain-modulated silicon avalanche photodiode synchronized with a mode-locked argon-ion laser is used as the main component of a direct reading high-sensitivity flourescence lifetime detector with 10 ps time resolution and 2 photoelectrons per laser period sensitivity. Fluorescence lifetimes τ_f = 10 psto 10 ns of single exponential processes are indicated directly. Moreover, the detector can be used to measure τ_rot or one unknown parameter in a mixture of two fluorophores.