Frequency Comb Velocity-Modulation Spectroscopy
  We have demonstrated a new technique that provides massively parallel comb spectroscopy sensitive specifically to ions through the combination of cavity-enhanced direct frequency comb spectroscopy with velocity modulation spectroscopy. Using this novel system, we have measured electronic transitions of HfF+ and achieved a fractional absorption sensitivity of 3 x 10-7 recorded over 1500 simultaneous channels spanning 150 cm-1 around 800 nm with an absolute frequency accuracy of 30 MHz (0.001 cm-1). A fully sampled spectrum consisting of interleaved measurements is acquired in 30 minutes. 
Laura C. Sinclair, Kevin C. Cossel, Tyler Coffey, Jun Ye, and Eric A.   Cornell
physics.atom-ph physics.chem-ph physics.optics