Double excitations of helium in weak static electric fields.
A dramatic electric field dependence has been observed in the fluorescence yield spectrum of the doubly excited states in helium, where a rich phenomenology is encountered below the threshold. Fluorescence yields of certain states can be tuned to zero, while other dipole-forbidden states are significantly enhanced, for fields much weaker than 1 kV/cm. Using an R-matrix multichannel quantum defect theory, spherical-to-parabolic frame transformation method, we are able to reproduce the main features of the observed spectrum, and we discuss the qualitative behavior in terms of weak electric field mixing.
Physics Department, Box 530, S-751 21 Uppsala, Sweden.
Conny
C
Såthe
Magnus
M
Ström
Marcus
M
Agåker
Johan
J
Söderström
Jan-Erik
JE
Rubensson
Robert
R
Richter
Michele
M
Alagia
Stefano
S
Stranges
T W
TW
Gorczyca
F
F
Robicheaux