Energy transfer reaction K(4s) + K(7s) \rightarrow K(4s) + K(5f), theory compared with experiment

A comparison between theory and experiment, concerning the K(4s)+K(7s)\rightarrow K(4s)+K(5f) reaction of energy transfer in thermal collisions, is presented. Relevant cross sections are calculated for the potassium vapour temperatures in the range of 310-1000 K. They are based on the theoretical adiabatic K_2 potential energy curves and on the use of the multicrossing Landau-Zener model. In the temperature range of the present experiment, 428-451 K, the computed cross sections vary little, from 2.09x10^-14 cm^2 to 2.04x10^-14 cm^2, and agree well with the value 1.8(8)x10^-14 cm^2, which is the average of the corresponding experimental results.

Energy transfer reaction K(4s) + K(7s) → K(4s) + K(5f), theory compared with experiment

Abstract A comparison between theory and experiment, concerning the K(4 s) + K(7s)→K(4 s) + K(5f) reaction of excitation energy transfer in thermal collisions, is presented. The cross sections for this process are calculated for the potassium vapour temperatures in the range of 310–1000 K. The calculations are based on the theoretical adiabatic K2 potential energy curves and on the use of the multicrossing Landau-Zener model. The experiment was carried out using the method of spectroscopy with resolution in time. The signals of the direct-fluorescence decay from pulsed-laser-excited 7s state, and of the sensitized-fluorescence from 5f state, were registered and analysed. In the temperature …

Vibrational effects in Na2( , v′)+Na(3p3/2) associative ionization

Abstract Associative ionizing Na2( A 1 Σ + u , v′)+Na(3p3/2) collisions have been studied in a single supersonic beam with respect to the influence of the initial vibrational excitation of the molecules on the reaction efficiency. An enhancement of trimer ion yield of nearly one order of magnitude has been observed as the vibrational excitation increases from v′=0 to v′=14.

Fine-structure mixing collisions of Rb(52D) excited in a two-photon transition using external-cavity cw diode laser

We present an experimental study of fine structure (fs)- mixing in the 5 2 D state of Rb, and details of construction and performance of an external cavity cw diode laser, developed to provide a light source at 778 nm for two-photon excitation of Rb(5 2 D). Cross section for the fs-mixing Rb(5 2 D 5/2 ) yields Rb(5 2 D 3/2 ) in collisions with the ground state Rb(5 2 S 1/2 ) atoms was found to be 5.8 +/- 1.9 (DOT) 10 -14 cm 2 .

Vibrational relaxation of Na2 molecules in a triplet state: collisional transfer from a mixed A 1Σu+ − b3Πu gateway level to long-lived levels of b 3 Πu

Abstract Collision-induced vibrational transitions of Na2 within the b 3Π1u state have been observed in a free jet expansion, using two CW dye lasers for the pump and probe steps. The b-state is entered by the pump laser using a low mixed ( A 1 Σ u + − b 3 Π u ) level as a gateway. The occupations of various v′,J′-levels are studied as functions of the position in the flowing gas. The radiative lifetimes of Na2 in levels which had been populated by vibrational relaxation are found to be very long (> 4 μs). Cross-sections are estimated for vibrationally inelastic collisions with Na and Ar atoms.

Quasi-resonant energy transfer in collisions: Na2(A1? u + )+K(4S)

Cross sections for electron energy transfer from the initial rotational stateJ′of the two lowest vibrational levelsv′=0 andv′=1 of excited dimers Na2(A) to potassium atoms as described by Na2(A1Σu+,v′J′)+K(4S)→Na2 (X1Σg+,v″J″)+K(4P)+ΔE have been examined by laser-induced fluorescence. A strong increase of the cross section by as much as an order of magnitude has been observed for those dimerv′J′-levels for which the dipole transitions are close to resonance of the 4S-4P transitions in the atom (ΔE<4 cm−1). The absolute cross sections for energy transfer have been calculated by the Rabitz approximation of first-order perturbation theory. In the case of closest energy resonance (ΔE=0.9 cm−1) …

Excitation transfer between the rubidium52Dfine-structure levels in collisions with ground-state rubidium atoms: Experiment and theory

Experimental and theoretical study of thenf-level lifetimes of potassium

The theoretical and experimental values of the 5f ,6 f ,7 f, and 8f radiative lifetimes of neutral potassium are reported. The reduced matrix elements for all allowed electric-dipole nf5/2-nd5/2, nf5/2-nd3/2, and nf7/2-nd5/2 transitions with n =5–8 in K arecalculated 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 ,6 f ,7 f, and 8f states in neutral K and their uncertainties. The contributions from the nf5/2-ng7/2, nf7/2-ng7/2, and nf7/2-ng9/2 transitions to the lifetimes o…

Studies of inelastic cross-section in Rb(7S) + Rb(5S) collisions

The cross section σ = (8 ± 4) × 10−15 cm2 was determined for the Rb(7S) + Rb(5S) → Rb(5D) + Rb(5S) excitation energy transfer process, and the quenching cross section σq = (2 ± 1) × 10−14 cm2 for the Rb(5D) state in collisions with ground state Rb atoms. Applying rubidium quasimolecular asymptotic potential curves at relatively large internuclear distances, a qualitative interpretation of the experimental results is presented. It is shown that the quenching of the Rb(5D) atoms in collisions may be explained by a reversed energy pooling process Rb(5D) + Rb(5S) → Rb(5P) + Rb(5P).

All-experimental values of self-quenching cross-sections for nf states (n=5-8) of potassium atoms

All-experimental self-quenching cross-sections σ nf are reported for K(nf) states (n = 5, 6, 7, 8). The experiment was performed at varied temperatures of K vapour in a spectral cell. Time-resolved fluorescence was observed following pulsed step-wise excitation with dipole and quadrupole transitions K(4s) → K(4p) → K(nf). The values: σ 5f = 2.4 ± 1.7, σ 6f = 4.5±1.4, σ 7f = 8.1±1.8, and σ 8f = 18.2±3.0 (in units of 10−13 cm−1) were obtained from a Stern-Volmer-type plot.