Atomic Physics and Spectroscopy During the First 50 Years of JPCRD

Atomic spectroscopy and atomic physics papers represent a significant part of publications in Journal of Physical and Chemical Reference Data (JPCRD). Critical compilations of spectroscopic data, accurate calculations of collisional parameters, and bibliography on spectral line profiles and shifts provided much needed information for plasma physics, astrophysics, lithography, fusion research, and other fields of science. We present a brief overview of the atomic physics research published in JPCRD over its first 50 years.

Simulations of Gamma Cascades and Modelling Atomic Collision Chains

A new method for simulation of nuclear γ cascades by the Monte Carlo technique is described. It makes it possible to generate artificially individual events of the γ-cascade decay of neutron capturing states in heavy nuclei. For the purpose of determination of lifetimes of nuclear levels by the GRID method the previously developed Mean Free Path Approach for modelling atomic collisions and their interplay with cascades has been generalized. Examples of the use of this generalization for determination of lifetimes of selected (150)Sm and (158)Gd levels are given and discussed.

The GRID Technique: Current Status and New Trends

In the GRID technique one measures Doppler-broadened line profiles of γ transitions using the high resolution crystal spectrometers GAMS, which are installed at the high flux reactor of the ILL Grenoble. One of the essential applications of this technique is the measurement of nuclear state lifetimes. In the present contribution the precision and the principal limits of the technique are discussed.

Study of Interatomic Potentials in ZnS-Crystal-GRID Experiments Versus Ab Initio Calculations

Crystal-GRID measurements have been performed with ZnS single crystals. For the first time, an asymmetric Crystal-GRID line shape could be observed. The preliminary data evaluation indicates that the reported lifetime of the 3221 keV level in (33)S is too short. A value of about 60 fs has been found. Due to this "long" lifetime the line shape is much less structured than calculated with the reported lifetime.