  A recent proposal by Maris[1], that single electron bubbles in helium might
fission into separate, particle-like entities, does not properly take into
account the failure of the adiabatic approximation when, due to tunneling,
there is a long electronic time scale. The point along the fission pathway of a
photoexcited p-state bubble, where the adiabatic approximation first breaks
down, occurs well before the bubble waist has pinched down forming two
cavities. In the connected two-lobed geometry, the p- and s-states are strongly
mixed by an antisymmetric vibrational mode, and the excitation decays by the
mechanism where one lobe collapses while the other expands into the spherical
s-state geometry. The extreme pressure jump in a photoexcited bubble leads to
shock formation that may halt the elongation even before adiabaticity is
compromised. In this case, the photoexcited bubble decays radiatively from the
relaxed p-state geometry.
  [1] H.J. Maris, On the fission of elementary particles and the evidence for
fractional electrons in liquid helium, J. Low Temp. Phys. 120, 173 (2000)
