Z. S. Li

Radiative lifetimes in La III and oscillator strengths in La III and Lu III

New radiative lifetime measurements performed with time-resolved laser spectroscopy for the 6p1/2 and 6p3/2 levels of La III provide a unique opportunity for testing the adequacy of the relativistic Hartree-Fock approach for atomic structure calculations in this ion. As a consequence of the comparison, an extensive set of accurate f-values is provided for many La III and Lu III UV and visible transitions of astrophysical interest.

Experimental and theoretical energy levels, transition probabilities and radiative lifetimes in Yb III

The analysis of the spectrum of Yb III has been extended allowing us to establish 11 new energy level values. In addition, radiative lifetimes of two excited states of Yb III have been measured for the first time using time-resolved laser-induced fluorescence following two-photon excitation. The good agreement between experimental results and semi-empirical calculations performed with the relativistic Hartree-Fock method including core-polarization effects allows the determination of transition probabilities for 15 lines.

Radiative lifetime measurements in Tm III with time-resolved laser spectroscopy and comparisons with HFR calculations

Natural radiative lifetimes of eight levels in Tm m were measured with the time-resolved laser-induced fluorescence (LIF) technique. Free doubly ionized thulium ions were obtained in a laser-produced plasma. Three even-parity levels were excited from the ground state with one-photon excitation, using a laser system generating pulses of 1 ns duration. Five odd-parity levels were excited from the ground state with two-photon excitation, where a picosecond laser system was employed. In both cases, the lifetimes were evaluated from transient LIF signals detected with a fast-detection system. The experimental lifetime results were compared with Hartree-Fock calculations including relativistic corrections. Good agreement was achieved for the 4f(12)6p levels while larger discrepancies are noted for some 4f(12)5d levels. (Less)

Lifetimes and Oscillator Strengths for Ultraviolet Transitions in Neutral Sulfur

A consistent set of f-values for vacuum ultraviolet lines of S I is deduced from a combination of laser lifetime measurements and theoretical branching ratios. The new results are compared with results deduced from absorption by interstellar gas toward zeta Ophiuchi, and good agreement is observed for most transitions.

Lifetime measurements in Yb II with time-resolved laser spectroscopy

Natural radiative lifetimes of 10 levels of singly ionized ytterbium have been measured with time-resolved laser spectroscopy. Free Yb+ ions were produced in a laser-induced plasma. A stimulated Brillouin scattering technique has been used to produce laser pulses as short as 1 ns for the excitation of short-lived Yb+ states. Pseudo-relativistic Hartree-Fock calculations, taking into account the core-polarization effects, have also been performed. A good agreement of the measured and the calculated lifetime values has been achieved.

Landé factor and lifetime measurements in even-parity Rydberg series of Pb I using time-resolved laser spectroscopy

Lande gJ factors and lifetimes for the levels in the even-parity Rydberg series 6pnp (n = 9-16) and 6pnf (n = 6-12) as well as for the levels from perturbing configurations of neutral lead have been measured using laser-induced fluorescence and Zeeman quantum-beat techniques. Two-step excitation was performed in a thermal atomic lead beam. Strong perturbations in the Rydberg series are manifested both in the gJ factor and lifetime data.