The measurements of the hyperfine structure of free, naturally occurring, alkali atoms are reviewed. The experimental methods are discussed, as are the relationships between hyperfine structure data and other atomic constants.

The basic concepts of quantum mechanics can be introduced at a high school level by considering the action of classical mechanics and then introducing Planck's constant as the granularity of that action. A practical example of the periodic motion of a spring allows students to investigate the limits of classical mechanics, and concepts such as the Uncertainty Principle can be discussed.

Temperature measurements in an automobile engine running in normal operating conditions have been obtained by observing the CARS spectra of molecular nitrogen. Pulsed lasers and a broad-band technique have been used to allow the single-pulse measurements necessary for studying combustion behaviour and cycle-to-cycle fluctuations. A fitting technique has been used to determine temperatures from the experimental data, with an uncertainty of about 50 to 100K. The authors discuss the problems that are still unresolved in order to achieve better accuracy: beside experimental refinements a further knowledge of molecular parameters seems to be required.

No abstract