Typical ATI spectrum

Absorbed Photons

P. H. Bucksbaum  PRA 37  3615  (1988)

ħω

ħω

ATI peaks

ponderomotive energy

Ionization potential

0         5         10         15         20        25         30

Helium   I= 2.3 x 1014 W/cm2                   = 8  ps,    532  nm