Measurement of the ground-state Lamb shift of hydrogen-like Ti21+

Abstract
Using an electron beam ion trap (EBIT) and a crystal spectrometer in the Johann geometry, the 1s Lamb shift of hydrogen-like Ti21+ has been measured; the result is L(1s) = 2.29(14) eV, in agreement with the theoretical value. The measurement was made by calibrating the Lyman-α wavelengths using the characteristic Kα wavelengths of neutral vanadium. The Kα spectrum was produced by inserting a wire probe near the electron beam of the EBIT. While the present measurement is preliminary, achieving only modest precision, it suggests that much higher precision could be achieved in the future.