Cascading Anticrossings fromn=5 He+

Electric-field-induced anticrossing signals of $n=5\mathrm{} {\mathrm{He}}^{+}$ are detected by intensity changes of the line He II 4686 Å ($n=4\mathrm{}$ to $n=3\mathrm{}$). The fine structure splittings $5^2{S}_{\frac{1}{2}}-5^2{G}_{\frac{7}{2}}$ and $5^2{S}_{\frac{1}{2}}-5^2{\mathrm{G}}_{\frac{9}{2}}$ have been derived from the measurements to be 15 924.4 ± 5.9 and 17 040.5 ± 8.0 MHz, respectively, in agreement with the theoretical values of 15 920.0 and 17 043.6 MHz. The splitting $5^2{G}_{\frac{7}{2}}-5^2{G}_{\frac{9}{2}}$ is 1116.1 ± 14.0 MHz compared with the theoretical value of 1123.6 MHz.