The site of the s-process was unambiguously determined when the unstable element Tc was observed in the spectra of a certain type of red giant (AGB) star. The distinction between the two processes is made by whether or not there is time for beta-decay to occur between the addition of subsequent neutrons. Roughly half of the n-capture isotopes are made in the s(low)-process and the other half in the r(apid)-process. This is because fusion becomes endothermic beyond Fe where the binding energy per nucleon peaks. Elements heavier than the Fe-group elements are made, almost entirely, via n-capture. Lab astro, specifically improved atoms transition probabilities, is playing a key role in new studies of the Galactic chemical evolution. There are good opportunities to extend similar research to other wavelength regions. The UW laboratory results almost always are directly linked to astronomical chemical composition efforts. These programs generally use time-resolved laser-induced-fluorescence (TR-LIF) to accurately measure total decay rates and data from high resolution Fourier transform spectrometers (FTSs) to determine emission branching fractions (BFs). The UW program is one of several productive efforts on atomic transition probabilities. The laboratory astrophysics program at the University of Wisconsin - Madison (UW) concentrates on neutral and singly-ionized species transitions that are observable in astronomical spectra of cool stars, emphasizing the rare earth n(eutron)-capture elements and the Fe-group elements that are important inputs to early Galactic nucleosynthesis studies.
The development of tunable dye lasers and a simple atomic and ionic beam source for all elements were critical in establishing a reliable absolute scale for atomic transition probabilities in the optical to near UV regions.
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