Shape Resonances in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>K</mml:mi></mml:math>-Shell Photoionization of Diatomic Molecules

Abstract

We show that $K$-shell photoionization spectra of diatomic molecules can exhibit strong shape resonances near threshold. The molecular field is decisive in this phenomenon. It induces the resonant contraction of high-$l$ components of the ionization channels, and it couples these components with low-$l$ components produced in the atomic cores by $K$-shell photoionization. We demonstrate the effect for ${\mathrm{N}}_{2}$ by using the multiple-scattering model. Clear evidence for this phenomenon exists for ${\mathrm{N}}_{2}$, CO, and NO.