The second spectrum of 136Xe has been excited by an especially devised technique so as to yield spectral lines of homogeneity sufficient to achieve interference orders up to several hundred thousand without actually reaching the limit. The pendant reservoir bulb of a microwave-excited electrodeless tube is sprayed with a jet of liquid nitrogen so as to attain a very low but extremely critical pressure condition, monitored by visual spectroscopic observation. Fully verified wavelengths of 108 lines have been established. Patterns of nine additional lines have been measured. The relative values of most of the levels that exhibit inter-combinations within the spectral range of the observations (3800–6500 Å) have been reevaluated on the basis of an unbroken array. These values include 5s25p4(3P) and 5s25p4(1D) systems.
CURTIS J. HUMPHREYS and EDWARD PAUL, JR., "Interferometric Wavelength Determinations in the Second Spectrum of 136Xe," J. Opt. Soc. Am. 60, 1454-1457 (1970)