A very great deal of work has been done during the last three years on the determination of atomic transition probabilities, and complete coverage here is impossible. Wiese and his staff at the National Bureau of Standards, Washington, have continued to collect all numerical results, and they can supply information as to what is available for any particular atom. They have published (1) a critical compilation of atomic transition probabilities for the atoms sodium to calcium (inclusive) in essentially the same way as an earlier compilation covered hydrogen to neon. At the time of writing a complete new bibliography is also in preparation (2), which will be published as NBS Special Publication 320 and which is complete up to June 1969. Review articles published include that of Layzer and Garstang (3) on theoretical allowed and forbidden transition probabilities, and the two volume conference report (4) covers beam foil spectroscopy (including lifetime measurements) in some detail. A fairly complete review of forbidden line transition probabilities was given by Garstang (5), where references to many original papers may be found. In the following we shall confine ourselves to mentioning a few areas of particular interest; detailed references can be traced through the bibliographies, reviews and abstracting journals.
Improved Atomic Transition Probabilities for UV and Optical Lines of Hf II and Determination of the Hf Abundance in Two Metal-poor Stars*
