Wavelength measurements of n=3 to n=2 transitions in neonlike Xe'"^, La' ! ''. Nd 5

The intercombination lines of the zinc sequence corresponding to the transition 4s 4p P l 4s 'S0 have been observed for xenon, lanthanum, neodymium, europium, gadolinium, and ytterbium in the Princeton Large Torus tokamak discharges.In one of the last experiments conducted on the Princeton Large Torus (PLT) tokamak, a number of elements in the rare-earth group were introduced into the discharge, and their spectra were observed with a variety of spectroscopic instrumentation.While a large number of spectra containing a multitude of lines were observed, their analysis will take a considerable time. However, in all the observed spectra the zinc and copperlike resonance lines were prominent. Their wavelengths are at least approximately in agreement with observations by Reader and Luther ' and Acquista and Reader in laser-produced plasmas. In addition to these, the zinc-sequence intercombination lines, which would not be observable in the highdensity short-duration laser-produced plasmas, were quite substantial, and they are the subject of the present paper.In these experiments the electron temperature of the Ohmically heated plasma ( -2 keV) was raised by adding about 0.6 MW of radio-frequency power near the lower hybrid frequency resulting in a fairly sharply peaked radial temperature profile with peak values 4.5-6.0 keV.The electron density profile was considerably broader with peak values (1-2)X10' cm . The rf pulse lasted for about 200 msec, and about 50 msec after its start the element in question was introduced by means of the laserablation technique.The lines in question were observed mostly by means of a Spex Industries bichromator. The wavelength accuracy, checked by observing nearby iron and carbon lines that are intrinsic in the plasma, is about 0.2 A or better.The lines were identified by their time behavior relative to the resonance line of the same ion species. Their intensities were of the order of 0. 1 x the corresponding resonance line, but no systematic variation could be established.Some of the lines were also observed with a grazing incidence polychromator, with the improved wavelength accuracy of about~0.1 A. Xenon was puffed into some of the discharges and its line established by analogous means.