Lifetime studies of alkali nf-levels.

Lifetimes of the 5f, 6f, 7f, and 8f states of potassium have been studied both theoreticaly and experimentally. The reduced matrix elements for all allowed electric-dipole nf_5/2-n'd_5/2, nf_5/2-n'd_3/2, and nf_7/2-n'd_5/2 transitions with n=5-8 in K were calculated using the relativistic linearized coupled-cluster method with single and double excitations of Dirac-Fock wave functions included to all orders in many-body perturbation theory. The resulting electric-dipole matrix elements are used to evaluate the lifetimes of the 5f, 6f, 7f, and 8f states in neutral K. The contributions from the nf_5/2-n'g_7/2, nf_7/2-n'g_7/2, and nf_7/2-n'g_9/2 transitions to the lifetimes of the 6f, 7f, and 8f states were evaluated using the third-order many-body perturbation theory and were found to be very small. The theoretical results are

τ_5f =117.4 ns;

τ_6f =195.4 ns;

τ_7f =301.6 ns;

τ_8f =441.9 ns.

The experimental values were obtained form an experiment in a vapour cell using time-resolved fluorescence measurements upon pulsed two-step excitation scheme 4s→4p→nf. The measured values

τ_5f =117.3 ns;

τ_6f =190.6 ns;

τ_7f =309.8 ns;

τ_8f =428.1 ns

are in excellent agreement with the present theoretical calculations. The results are published in [1]. Collisional quenching cross-sections of the nf states with n = 5-8 were also measured as (in units of 10^-13 cm²) σ_q = 2.4±1.7; 4.5±1.4; 8.1±1.8, 18.2±3.0, respectively [2].

[1] M. Głódź, A. Huzandrov, M. S. Safronova, I. Sydoryk, J. Szonert, and J. Klavins, Phys. Rev. A 77, 022503 (2008);

[2] M. Głódź, A. Huzandrov, I. Sydoryk, J. Szonert, and J. Klavins, Acta Phys. Pol. A 112, 1185 (2007). 

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Research activities

• Introduction
• Establishment of the Molecular Beam Laboratory and Laser Centre
• Population transfer to high-lying molecular levels.
• Lifetime and branching ratio measurements using the Autler-Townes effect
• Stochastic phenomena in collisions with Rydberg atoms.
• Stochastic behaviour of photons in absorbing media and its applications.
• Spectroscopic manifestation of radiation trapping in a supersonic beam.
• Ionization of Alkali-Metal Rydberg atoms by blackbody radiation.
• Manipulation of spatial distribution of excited molecules in a beam via dressed-state interference.
• Metastable Rydberg states and blocade effect.
• Stark switching of microwave field induced dynamic chaos regime.
• Line broadening due to optical pumping at unsaturated fields in atomic and molecular beams.
• Lifetime studies of alkali nf-levels.
• Conditions and limitations for resolution of hyperfine structure in the Autler-Townes spectra.
• Fluorescence decay at subnatural times in a magneto optical trap.
• Reconsideration of spectral line profiles affected by transit time broadening
  
• Population switching via interferences in the Autler-Townes effect
• Penning ionization of cold Rb Rydberg atoms due to long-range dipole-dipole interaction