Photoionisation loading of large Sr+ ion clouds with ultrafast pulses
  This paper reports on photoionisation loading based on ultrafast pulses of singly-ionised strontium ions in a linear Paul trap. We take advantage of an autoionising resonance of Sr neutral atoms to form Sr+ by two-photon absorption of femtosecond pulses at a wavelength of 431nm. We compare this technique to electron-bombardment ionisation and observe several advantages of photoionisation. It actually allows the loading of a pure Sr+ ion cloud in a low radio-frequency voltage amplitude regime. In these conditions up to 4x10^4 laser-cooled Sr+ ions were trapped. 
S\'ebastien Removille (MPQ), Romain Dubessy (MPQ), Quentin Glorieux   (MPQ), Samuel Guibal (MPQ), Thomas Coudreau (MPQ), Luc...