Heidi Milia Anderson

Radiative lifetimes in Tm i and Tm ii

New radiative lifetime measurements based on time-resolved laser-induced fluorescence are reported for 68 even-parity and 126 odd-parity levels of Tm i ranging in energy from 16 000 to 51 000 cm-1 and for 85 even-parity and 19 odd-parity levels of Tm ii, ranging in energy from 23 000 to 55 000 cm-1.

Multiline visible emission from a barium low-pressure discharge

A multiline visible emission spectrum, yielding “white” light, has been observed from a low-pressure Ba discharge. A five atomic level numerical model reproduces the observations qualitatively, suggesting that a low-pressure Ba discharge light source is capable of a significantly better color rendering than previously thought.

Radiometric efficiency of barium discharge plasmas

Summary form only given, as follows. Barium has a number of characteristics that indicate it may be a good atomic radiator in a glow discharge. Thus, a Ba glow discharge may prove to be of interest to the lighting industry for use in a novel, efficient light source. Progress in experimental determinations of the radiometric efficiency of a barium DC glow discharge under a variety of conditions will be reported.

Atomic data for lighting and astrophysical applications: excited-state lifetimes and transition probabilities for rare-earth elements

Summary form only given. Because of the extremely rich spectra of rare-earth metals, a large volume of data for these elements is sought by the lighting industry for modelling of a new generation of High-Intensity Discharge lamps. In addition, the observation of rare-earths in the atmospheres of chemically peculiar stars means that this data is also of substantial interest to the astrophysics community. We are currently meeting this need with a combination of two experiments: excited-state lifetimes are obtained from laser-induced fluorescence measurements on a slow atomic/ionic beam, and branching fractions are obtained with a Fourier-transform spectrometer. These two sets of data are then combined to produce absolute transition probabilities (or, Einstein A-coefficients). This approach has been extremely fruitful in that, over the last year alone, 298 lifetimes and hundreds of transition probabilities have been measured to better than 5% and 10% accuracy, respectively, for neutral and singly-ionized thulium. (The strongest lines are emphasized in this first set of measurements.) Obtaining high-quality data of this nature has involved the development of an appropriate atomic beam source, as well as a careful understanding and elimination of a variety of systematic effects. Current work has yielded preliminary lifetime measurements on more than 400 levels of neutral and singly-ionized dysprosium, and will eventually continue with holmium.