Polarization effects in collision-induced intramultiplet mixing for neon (Ne**){(2p)5(3p)} + helium

High-quality polarized-emission cross sections for the {a}5=|J=1,MJ>¿{a}7 and {a}5¿{a}4 transitions in the {a}={(2p)5(3p)} multiplet (lifetime 20 ns) have been measured in a crossed-beam experiment. For the {a}5¿{a}7 transition we observe a strong preference for the |MJ|=0 orientation. The small cross section for the |MJ|=1 orientation can be understood qualitatively from the model potentials of Hennecart and Masnou-Seeuws by the strong coupling to the {a}4 and {a}6 states (avoided crossings), which is absent for the O=|MJ|=0- molecular potentials because of the constraint of reflection symmetry