Excess-photon detachment of negative chlorine ions with 100 fs laser pulses

Multiphoton detachment spectra of Cl-, showing excess-photon absorption, have been obtained using short (100 fs) and intense (up to 5*1016 W m-2) optical pulses with a wavelength of 620 nm. In the short-pulse regime the shifts in the electron spectrum can be related directly to shifts of the continuum states. In this way, it is shown experimentally that excess-photon detachment can occur in the absence of channel closure.