Stark transitions in antiprotonic helium

Collisional Stark rates for (p) over bar He-4(+) with 36less than or similar tonless than or similar to38 are estimated with coupled-channel calculations. Both an atomic and a molecular model are used. Matrix elements of the (p) over bar He+-He interaction for the atomic model are approximated with expressions having two or three parameters. Rough estimates for the molecular model are obtained using the generalized Born-Oppenheimer approximation, together with matrix elements for the atomic model. Guesswork, based on interactions of seemingly similar atoms, is used to set fairly wide limits to parameters for the atomic model, it being assumed that the potentials depend only on n, l, and R. Transitions are found to be unlikely. But the rates are sensitive to the potentials. Transitions can be likely if the potentials are different from what can reasonably be guessed by assuming a dependence on only n, l, and R. A potential with a minimum, preferably relatively deep, at relatively small R can cause transitions to be important. It is conjectured that this can occur because (p) over bar He+-He potentials depend on the component of (p) over bar He+ intrinsic angular momentum along R. Also, it is found that the difference in the reduced mass of (p) over bar He+ and He can cause the rate to be several times higher for (p) over bar He-3(+) than for comparable (p) over bar He-4(+).