Double photoexcitation of helium in a strong dc electric field.
We report the first experimental measurements of the effect of an applied field on the photoexcitation and autoionization of doubly excited states of helium. Ground-state photoionization spectra have been measured in the region below the He+(N=2) threshold with static electric fields of up to 84.4 kV/cm across the interaction region. The results are compared to the theoretical calculations of Chung et al. [J. Phys. B 34, 165 (2001)]], which are the only calculations available in this regime. Transitions to several states in the N=2, n=6 manifold are assigned, and a wealth of new structure is observed. Our data show that many more series are mixed in by the field than those predicted by theory.
Harries
James R
JR
Photon Factory, IMSS, KEK, 1-1 Oho, Tsukuba-shi, Ibaraki-ken, 305-0801 Japan.
Sullivan
James P
JP
Sternberg
James B
JB
Obara
Satoshi
S
Suzuki
Tadayuki
T
Hammond
Peter
P
Bozek
John
J
Berrah
Nora
N
Halka
Monica
M
Azuma
Yoshiro
Y