The momentum transfer dependence of fundamental double excitation processes of helium is studied by absolute measurements using an angular resolved fast-electron energy loss spectrometer with high energy resolution. It elucidates the dynamical correlations, in terms of internal correlation quantum numbers, $\mathcal{K}$, $\mathcal{T}$, and $A$. The Fano profile parameters $q$, $f_a$, ${\rho }^2$, $f$, and $S$ of doubly excited states ${}_2(1,0{)}_2^{+}{}^{1}S^e$, ${}_2(1,0{)}_2^{+}{}^{1}D^e$, and ${}_2(0,1{)}_2^{+}{}^{1}P^o$ are reported as functions of momentum transfer $K^2$. Qualitative analysis is given for the states of ${}_2(-1,0{)}_2^{+}{}^{1}S^e$ and ${}_2(1,0{)}_2^{+}{}^{1}S^e$.

• Received 6 February 2003

DOI:https://doi.org/10.1103/PhysRevLett.91.193203