Interatomic potentials, which include bond-bending terms, allow us to model accurately the properties of &-quartz and the structures of other polymorphs of Si02.

Two-photon polarization spectroscopy is an established method for making excited state symmetry assignments in randomly oriented samples. The relationship between the two-photon absorption process and the symmetry of the excited state, as established by previous theoretical developments, is illustrated in terms of the principles of the interaction between polarized light and oriented symmetric molecules. A description of the experimental methodology is presented and several applications for which this method has been used in vibronic coupling studies are discussed.

Bandwidth-limited pulses of 2.5 ps in duration are reported for a cavity-dumped synchronously pumped dye laser when saturable absorber is mixed with the laser dye. The pulses are tunable over a 610–640-nm range, and the energy per pulse is in the range of 4–8 nJ.