Predissociation dynamics of D2 + hv → D(1s1/2) + D(2p1/2,3/2, 2s1/2) revealed by the spin-orbit state resolved fragment branching ratios and angular distributions

Photodissociation of HCl in the photon energy range 14.6-15.0 eV: Channel-resolved branching ratios and fragment angular distributions

For the HCl molecule, four photodissociation channels are open in the excitation energy region 14.6-15.0 eV: H(2s) + Cl(²P_3/2), H(2p) + Cl(²P_3/2), H(2s) + Cl(²P_1/2), and H(2p) + Cl(²P_1/2). We measured the fragment angular distributions and the branching ratios of the four dissociation channels by using the extreme ultraviolet laser pump and UV laser probe, delay-time-curve, and velocity map imaging methods. The channel-resolved fragment angular distributions and fragment yield spectra show that various Rydberg states (superexcited states) contribute to the absorption cross sections, including the [A²Σ⁺]4pσ, [A²Σ⁺]4pπ, [A²Σ⁺]3dσ, [A²Σ⁺]3dπ, and [A²Σ⁺]5sσ states. Most of the H(2s) + Cl(²P_1/2) channels correlate with the ¹Σ⁺ states, while the other channels correlate with mixing excitations of the ¹Σ⁺ and ^1,3Π states. The channel branching ratios are dependent on the excitation energies. When the four channels are open, the channel branching ratios of H(2s) + Cl(²P_3/2) and H(2p) + Cl(²P_1/2) are small. Based on the recent ab initio potential energy curves, the Rydberg states converging to the ion-core A²Σ⁺ are proposed to be predissociated by the nuclear vibrational continua of the Rydberg states converging to the ion-core X²Π.