Spectroscopy of ³P⁰ states of alkaline earths

Using multiphoton-ionization spectroscopy, we have observed transitions from the 1S0 ground states to the 4snp, 5snp, and 6snp 3P0 states of the alkaline earth atoms Ca, Sr, and Ba, respectively. One-photon transitions from a 1S0 ground state to 3P0 states are spin-forbidden. We have identified these series in Ca and Sr up to n > 70, whereas previous efforts have failed to identify these series beyond n = 7. These series behave like nearly constant quantum-defect (δ) series with δCa = 1.97 and δSr = 2.90. Preliminary results for Ba, up to n = 60, indicate greater complexity. © 1977 (publisher). All right reserved.