Lifetime measurement of the T=23 537 cm-1, J=9/2 odd-parity level in Nd II using time-resolved collinear fast-beam laser spectroscopy.

Abstract

Time-resolved collinear fast-beam laser spectroscopy has been used to measure the lifetime of the T=23 537 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, J=9/2 odd-parity [abbreviated as (23 537)${\mathrm{\ifmmode^\circ\else\textdegree\fi{}}}_{9/2}$] level in Nd ii. Nanosecond pulsed excitation was achieved with the Doppler switching technique. The fast ions were selectively excited from the metastable 4${\mathit{f}}^{4}$5d $^{6}$${\mathit{K}}_{9/2}$ level to the (23 537)${\mathrm{\ifmmode^\circ\else\textdegree\fi{}}}_{9/2}$ level by the light of a cw dye laser. The decay of the resonance fluorescence photons emitted in the transition to the ground 4${\mathit{f}}^{4}$6s $^{6}$${\mathit{I}}_{7/2}$ level, as a function of the flight distance, was observed. The decay length was scaled into the decay time by the ion velocity, which was determined using the optical resonance itself. The lifetime is 27.7(9) ns.