Photodissociation cross sections ofAr2+,Kr2+, andXe2+from 6200 to 8600 Å

Abstract

The photodissociation (photoabsorption) cross sections of ${\mathrm{Ar}}_{2}^{+}$, ${\mathrm{Kr}}_{2}^{+}$, and ${\mathrm{Xe}}_{2}^{+}$ have been measured from 6200 to 8600 \AA{}. The rare-gas dimer ions were produced in a drift-tube mass spectrometer and irradiated by a dye laser. The wavelength dependence of the photodissociation cross sections, which is similar for all three dimer ions, reflects a direct dissociation process. The broad maxima of ${\mathrm{Ar}}_{2}^{+}$, ${\mathrm{Kr}}_{2}^{+}$, and ${\mathrm{Xe}}_{2}^{+}$ occur at 7200, 6850, and 7000 \AA{}, respectively, with cross sections of 0.19, 2.9, and 12\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}18}$ ${\mathrm{cm}}^{2}$. The processes for formation of dimer ions in the drift tube are discussed. It is concluded that the ions are essentially in thermal equilibrium near 300\ifmmode^\circ\else\textdegree\fi{}K at the time of photon interaction. The present photodissociation cross sections of ${\mathrm{Ar}}_{2}^{+}$ and ${\mathrm{Kr}}_{2}^{+}$ are in reasonable agreement with theoretical calculations based on recently determined potential curves.