Vibrational Cooper minima used to verify the dissociation pathway induced by a short intense laser pulse

Vibrational Cooper minima due to weak dipole coupling were previously observed in strong-field dissociation of ${\mathrm{H}}_{2}{}^{+}$ as minima in the kinetic-energy-release (KER) spectrum [McKenna et al., Phys. Rev. Lett. 103, 103006 (2009)]. We demonstrate in two independent experiments that these vibrational Cooper minima occur more generally and can be used as ``fingerprints'' to identify the final electronic state in the dissociation pathway. In the first experiment, we show the wavelength dependence of the vibrational Cooper minima observed in the KER spectrum of ${\mathrm{O}}_{2}{}^{+}$ dissociation induced by 396- and 264-nm photons. These minima appear at the locations predicted by our first-order perturbation-theory calculations. In the second experiment, a delay-dependent KER spectrum is obtained from ${\mathrm{O}}_{2}$ using an ionizing pump and a dissociating probe, then Fourier-transformed to generate a spin-rotation quantum beat spectrum of ${\mathrm{O}}_{2}{}^{+}$. This spectrum shows vibrational Cooper minima at the expected locations, confirming their presence in another observable. In this case, these minima are used to identify the dissociation pathway.