Ab initio analysis of autoionization of H-3 molecules using multichannel quantum-defect theory and new quantum-defect surfaces - art. no. 033410

Highly accurate Born-Oppenheimer potential-energy surfaces of H-3 were calc ulated and combined with multichannel quantum-defect theory (MQDT) to predi ct with high precision the photoionization cross section of laser-excited t riatomic hydrogen recently measured in this laboratory. The experiment firs t prepares H-3, in stepwise excitation in a;single rotational level of the symmetric stretch excited 3s Rydberg state. One-photon ionization from this state populates the continuum and np Rydberg states which autoionize into H-3(+) + e(-). In the vicinity of the first symmetric stretch excited level of H-3(+) the ionization spectrum shows features similar to those observed at the lowest ionization threshold, a quasidiscrete region below the first symmetric-stretch excited threshold. a Beutler-Fano region of rotational a utoionization and interlopers of low-n Rydberg states belonging to high vib rationally excited cores dispersed over the continuum. The MQDT calculation s include rotational, vibrational, and Jahn-Teller interactions, and permit the assignment of most of the spectral features.