Simplifying Spectra by Laser Level Labeling

Lasers can simplify spectra by increasing or decreasing the population of a chosen level or by orienting the molecules, so that transitions involving that level can be identified. These methods reveal several series of Rydberg states in Na 2 , from which the constants of the ground state of the ion can be extrapolated. Many c.w. two-photon transitions, strongly enhanced by near coincidence with allowed transitions, have been identified. Unusual line shapes are found when the offset from exact coincidence is much less than the Doppler line width.