Phase measurement of resonant two-photon ionization in helium.
We study resonant two-color two-photon ionization of helium via the 1s3p (1)P(1) state. The first color is the 15th harmonic of a tunable Ti:sapphire laser, while the second color is the fundamental laser radiation. Our method uses phase-locked high-order harmonics to determine the phase of the two-photon process by interferometry. The measurement of the two-photon ionization phase variation as a function of detuning from the resonance and intensity of the dressing field allows us to determine the intensity dependence of the transition energy.
Swoboda
M
M
Department of Physics, Lund University, P.O. Box 118, 22100 Lund, Sweden.
Fordell
T
T
Klünder
K
K
Dahlström
J M
JM
Miranda
M
M
Buth
C
C
Schafer
K J
KJ
Mauritsson
J
J
L'Huillier
A
A
Gisselbrecht
M
M