The spectroscopic investigations of lanthanide doped LaF^ crystals and their theoretical interpretation reported here are the result of an extensive joint effort of the Argonne National Laboratory and The Johns Hopkins University over the last decade. It had its roots in similar studies at both laboratories of other crystal hosts, particularly LaCl 3> for which a summary is also given in an appendix to this report. This work was supported at Argonne by the United States Atomic Energy Commission and the United States Energy Research and Development Administration, and at Hopkins by the United States Army Research Office and the National Science Foundation. An identical report is being issued under separate cover by each institution. ' vide the basis for computing the radiative lifetime for any given state in any ! > •'->-,• member of the series. Spectroscopic results for all lanthanides doped into LaF, (Ln :LaF,) ' ",,, > except Pm 3+ and Eu 3+ are reported. Since the crystals were obtained from S;-commercial sources, the fact that the only isotope of Pm available in macro-4amounts is ' Pm which is g"-unstable with a relatively short half-life, excluded it from consideration. The tendency of EuF 3 to reduce to EuF 2 at high temperatures even in the presence of F., vapors, and the very strong broad band 2+ structure associated with Eu in the visible and ultraviolet range due to 4f-+ 4f 5d transitions, made it impossible to obtain the requisite experi-3+ mental data for the Eu-system. The energy level schemes for Pm :LaFo and Eu :LaF_ were therefore calculated using parameters obtained by interpolation. Some of the experimental results utilized in the analyses represent as yet unpublished work done over a period of years in the Chemistry Division of Argonne National Laboratory with the help of senior thesis students and guest scientists. These results were obtained using several different instruments. Spectra in the range ^OOO-ieOOO cm" were recorded using a Cary Model 14R (crystal-grating-0.5 meter) recording spectrophotometer. In the region 15000-50000 cm, both a 1-meter Hilger-Engis Model 1000 spectrograph equipped with an EMI 9558 Q photomultiplier, and the Argonne 30' Paschen-Runge spectrograph (in second order) were used. Observations were made at ^298, 77, and 4 K. Crystals of LaF, doped with selected lanthanides in various concentrations were obtained from Optovac Inc., North Brookfield, Mass. 01535. There continues to be a wide interest in lanthanide-doped crystals and glasses as laser materials. In some cases quantitative intensity calculations-14-IV. Energy Level Correlations-Survey of Experimental Data The energy level structure in Pr :LaF, has been examined experimentally in moderate to high resolution by several groups. Wong et al. (1963a), Yen et al. (1964), Caspers et al. (1965a), Carnal! et al. (1969). Free-ion level energies are recorded in Appendix III together with the corresponding computed levels using parameters given in Appendix II. The weak point in the theoretical analysis is the assumption...

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Beginning in the 1930s, G.H. Dieke and his students carried out an extensive program of measuring the optical spectrum of molecular hydrogen and its isotopes. Parts of the work were published but the project was interrupted by Dieke’s death in 1965, with much of the latest and most accurate work unpublished. This paper gives the 27 488 lines of molecular deuterium, measured by Dieke, arranges the 8243 assigned lines into band systems, and derives rotational–vibrational energy levels for over 50 electronic states. It also derives energy levels from published vacuum ultraviolet spectra of D2.

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