title: Direct frequency comb spectroscopy of trapped ions.
abstract: Direct frequency comb spectroscopy of trapped ions is demonstrated for the first time. It is shown that the 4s ;{2}S_{1/2}-4p ;{2}P_{3/2} transition in calcium ions can be excited directly with a frequency comb laser that is up-converted to 393 nm. Detection of the transition is performed using a shelving scheme to suppress the background signal from nonresonant comb modes. The measured transition frequency of f=761 905 012.7(0.5) MHz presents an improvement in accuracy of more than 2 orders of magnitude.
authors: Laser Centre Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands. alwolf@few.vu.nl
authors: A L
authors: AL
authors: Wolf
authors: S A
authors: SA
authors: van den Berg
authors: W
authors: W
authors: Ubachs
authors: K S E
authors: KS
authors: Eikema