Production of alkaline earth metastable states by a discharge in a heat pipe

An experiment is described in which the first excited metastable states nsnp 3 P o and nsnd 3 D of the alkaline earths Mg, Ca, Sr and Ba are populated by a continuous discharge running through a metal vapor maintained by a heat pipe. The number of atoms obtained in these excited triplet states is large enough to allow the observation of the series members in a conventional atomic absorption experiment. The Argonne 30 foot Paschen-Runge spectrograph has been used to record the spectra with a 0.37 AA mm -1 reciprocal dispersion. The wavelength uncertainty of +or-0.002 AA gives improved wavelength values for many lines measured previously in emission and gives an energy scheme for the highest terms of the series nsn's 3 S 1 ,nsn'd 3 D and nsn'f 3 F 0 that is more accurate than previously reported. The variations of the quantum defect have been fitted and the ionization limits, extrapolated from the triplet series, are compared with those obtained from the long principal series ns 2 1 S 0 -nsn'p 1 P 1 0 .