Low autoionization rates in the[5dnf] J=4,5 doubly excited series in Ba i

In a cw laser spectroscopic experiment using a collimated atomic beam of barium we have excited the 5dnf J=4 and 5 autoionizing series. In transitions from the metastable 5d² ¹{G}₄$ level inherently narrow autoionization linewidths, down to a Doppler-limited value of 10 MHz, have been observed. Assignment of all observed 5dnf transitions has been made.