Radiative electron capture by fully stripped channeled light ions

The cross sections for radiative electron capture (REC) into the [ital K] shell of bare and H-like light ions of [sup 12]C, [sup 16]O, [sup 19]F, and [sup 32]S are measured at different energies, under channeling conditions using a Si single crystal as target. These cross section data using different projectiles are shown to fall on a universal curve when plotted against a scaled variable, the adiabaticity parameter [eta][sub [ital K]], of the collision systems. We have observed a definite difference in the cross section between the present solid target data and the available data for a gas target at the same [eta][sub [ital K]] value. This difference, along with the observed shift in the REC photopeak energy, suggests an ion-solid-state'' effect. Further, these observations, especially their [ital Z] dependence, are consistent with the predictions of the theory.