Dechanneling by gas bubbles in a solid

The dechanneling probability (bar p) for a particle hitting a bubble in a solid is evaluated theoretically in the case of planar channeling. This probability bar p is found to be independent of the radius of the bubble and of the energy of the particle. In the simple case of a harmonic potential, bar p is found equal to one minus (π/4)(c/b), where 2b is the interplanar distance and c the maximum allowed oscillation amplitude in the channel. This probability has been measured in the particular case of α particles and helium bubbles in aluminium. The experimental value bar p = 0.27 +- 0.09 compares reasonably well with the theoretical values: bar p = 0.34 for a harmonic potential, bar p = 0.24 for a more realistic potential. (author)