Isotope shift measurements in the spectrum of trebly ionized cerium (Ce IV)

Isotope shifts have been measured between 140 Ce and 142 Ce in two lines of Ce IV using a Fabry-Pérot interferometer and a hollow cathode source. The results were: λ 2457 Angstrom (6s 2 S 1/2 -6p 2 P 3/2 ) 97 ± 3 mK, and λ 2778 Angstrom (6s 2 S 1/2 -6p 2 P 1/2 ) 100 ± 3 mK. The isotope shift constant was estimated to be 144 ± 6 mK. Of this, only 24 mK is caused by the change in deformation; the shift caused by a genuine increase in nuclear size has the unusually large value of 120 mK. The light source developed for this work should be suitable for the measurement of hyperfine structure in other highly ionized spectra. The fourth spectrum was obtained by pulsing the d.c. excitation voltage to the source. A table of isotope-shift data for elements from Sr to Ce is discussed.