Vibrational State-Selective Resonant Two-Photon Photoelectron Spectroscopy of AuS– via a Spin-Forbidden Excited State

• Published in: The journal of physical chemistry letters Vol. 6; no. 4; pp. 637 - 642
• Main Authors: Liu, Hong-Tao, Huang, Dao-Ling, Liu, Yuan, Cheung, Ling-Fung, Dau, Phuong Diem, Ning, Chuan-Gang, Wang, Lai-Sheng
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 19.02.2015
• Subjects: photoelectron spectroscopy; vibrational state selection; gold sulfide; electrospray ionization; velocity-map imaging; cold anions
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.5b00053

Vibrational state-selective resonant two-photon photoelectron spectra have been obtained via a triplet intermediate state (3Σ–) of AuS– near its detachment threshold using high-resolution photoelectron imaging of cryogenically cooled AuS– anions. Four vibrational levels of the 3Σ– excited state are observed to be below the detachment threshold. Resonant two-photon absorptions through these levels yield vibrational state-selective photoelectron spectra to the 2Σ final state of neutral AuS with broad and drastically different Franck–Condon distributions, reflecting the symmetries of the vibrational wave functions of the 3Σ– intermediate state. The 3Σ– excited state is spin-forbidden from the 1Σ+ ground state of AuS– and is accessed due to strong relativistic effects. The nature of the 3Σ– excited state is confirmed by angular distributions of the photoelectron images and quantum calculations.