SEPARATING CHEMICAL ISOTOPES WITH A TABLETOP TERAWATT LASER has been demonstrated by researchers at the University of Michigan, providing a more compact alternative to the bulky techniques for extracting isotopes, and introducing a new method for making ultrapure thin films which can be used in electronic devices. Using a technique known as chirped pulse amplification (Update 154), University of Michigan researchers (Peter Pronko, 734-763-6008) produced laser pulses that deliver between 10 trillion and 1 quadrillion watts (10-1000 terawatts) of power per square centimeter for an extremely short instant--between 150 and 200 quadrillionths (10^-15) of a second. Aimed at a target inside a vacuum chamber containing the isotopes of interest, the pulse vaporized some of the isotopes, which escaped in the form of ions (charged atoms). Intense magnetic fields associated with the pulses exerted forces on the ions which deposited them at different locations on a nearby silicon disk depending on the isotope's weight. With their technique, the researchers separated boron-10 from boron-11 and gallium-69 from gallium-71. It's an open question if their technique will be feasible on the large scales required for separating isotopes at nuclear facilities, but the researchers are initially setting their sights on other applications, such as depositing pure thin films of isotopes directly onto microelectronic devices. (Pronko et al., Physical Review Letters, 27 September 1999; figure at www.aip.org/png)