The ultraviolet photodissociation of DCl: H/D isotope effects on the Cl(2P) atom spin–orbit branching

The photodissociation of jet-cooled DCl molecules subsequent to excitation in the long-wavelength tail of the first UV absorption band (A1Π1←X1Σ+) has been investigated at five wavelengths in the range 200–220 nm. Ground state Cl(2P3/2) and spin–orbit excited Cl∗(2P1/2) photofragments were monitored using (2+1) resonance enhanced multiphoton ionization in a time-of-flight mass spectrometer. The product branching fractions are reported and compared with previous experimental results and high-level quantum mechanical calculations for HCl and DCl. A significant H/D isotope effect in the branching fractions is found at all the studied wavelengths, in quantitative agreement with recent theoretical predictions.