X‐ray parametric conversion—two photons for one

Nonlinear optical effects with visible light have long been known; the first laser was developed 12 years ago. Now Peter Eisenberger and Samuel McCall of Bell Telephone Laboratories have demonstrated nonlinear optical effects at x‐ray frequencies. In an experiment that verifies the calculations of Isaac Freund and Barry F. Levine, Eisenberger and McCall have achieved the x‐ray analog of optical parametric conversion. They have shown that a single x‐ray photon of frequency ${\omega }_{\mathrm{p}}$ incident on a crystal can result in the coincidental emission of two x‐ray photons ${\omega }_1$ and ${\omega }_2,$ where ${\omega }_1{\mathrm{+\omega }}_2{\mathrm{\hspace{0.17em}=\hspace{0.17em}\omega }}_{\mathrm{p}},$ and the crystal as a whole takes up the recoil, so that both energy and momentum are conserved. A prime reason for interest in the result is the anticipation that the work might be extended to a mixed x‐ray–visible experiment that could reveal microscopic details of the behavior of outer‐shell electrons in these nonlinear interactions.

This article is only available in PDF format