Atomic Radiative Lifetimes Measured by Pulsed Laser Spectroscopy in the Uv/Vuv Spectral Region

Abstract Experimental lifetime measurements on free atoms and ions performed by using pulsed laser excitation in the ultraviolet and vacuum-ultraviolet spectral regions are presented. Different methods of laser pulse generation, atomization and light detection are described. A short summary of results obtained is also given. Future possibilities in determination of lifetimes and transition probabilities in the short wavelengths region are discussed.

Frequency-modulation spectroscopy with blue diode lasers

Frequency-modulation spectroscopy provides ultrasensitive absorption measurements. The technique is especially adaptable to diode lasers, which can be modulated easily, and has been used extensively in the near-infrared and infrared spectral regions. The availability of blue diode lasers now means that the accessible wavelength region can be increased. We successfully demonstrate wavelength-modulation spectroscopy and two-tone frequency-modulation spectroscopy for the weak second resonance line of potassium at 404.8 nm and for the transition at 405.8 nm in lead, starting from the thermally populated 6p(2) P-3(2) metastable level, information on the modulation parameters is obtained with a f…

We report on lifetime measurements of the 3d(5)(S-6)4s4p(P-3)y P-6 degrees states of Fe II using time-resolved vacuum ultraviolet (VUV) laser spectroscopy. A laser-produced plasma has been used as the source of free Fe+ ions. The tunable VUV radiation was obtained employing resonantly enhanced sum-difference four-wave-mixing of short laser pulses. We obtained tau((6)P(3/2)degrees) = 3.90(20) ns, tau((6)P(5/2)degrees) = 3.80(20) ns and tau((6)P(7/2)degrees) = 3.65(20) ns.

Oscillator strengths of sulphur 3s23p34s3So-3s23p34p3P transitions measured by time resolved two-photon laser spectroscopy

Oscillator strengths for the three 3s23p34s 3S1o-3s23p34p 3P0,1,2 transitions in neutral sulphur have been determined directly from lifetime measurements. Two-photon UV laser excitation and subsequent fluorescence detection have been used on atoms produced in a thermal sulphur beam or in a laser-driven plasma. A good agreement was found between data obtained in both schemes. The lifetime data obtained, τ(3P0) = 46.1(1.0) ns, τ(3P1) = 46.1(1.0) ns and τ(3P2) = 46.1(1.0) ns are compared with results of theoretical and experimental data from literature. The absorption oscillator strengths derived are f(3S1o-3P0) = 0.120(0.003), f(3S1o-3P1) = 0.360(0.008) and f(3S1o-3P2) = 0.600(0.013), respect…

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) …

Spectral scattering dependencies of controllable PLZT occluder for vision science applications

Summary form only given. PLZT ceramics have an unique property - a facility to change the light scattering efficiency with the applied electric field. This effect is well manifested especially in the visible, just where the transparency windows of PLZT begins. Formerly we developed eye occlusion devices for vision science applications to introduce a dynamic decrease of the image contrast in stereovision tests. In future we plan to construct, using controllable scattering in PLZT, an eye simulator to study cataract caused retinal image quality reduction. The present work reports on spectral dependencies of such an eye occluder studied with the double optical integrated sphere technique.

Photodynamic therapy of nodular basal cell carcinoma with multifiber contact light delivery.

To overcome the limited treatment depth of superficial photodynamic therapy we investigate interstitial light delivery. In the present work the treatment light was delivered using a system in which three or six clear-cut fibers were placed in direct contact with the tumor area. This placement was thought to represent a step toward general purpose interstitial PDT. Twelve nodular basal cell carcinomas were treated employing delta-aminolevulinic acid and 635 nm laser irradiation. Fluorescence measurements were performed monitoring the buildup and subsequent bleaching of the produced sensitizer protoporphyrin IX. The treatment efficacy, judged at a 28-month follow-up, showed a 100% complete re…

Landé factor and lifetime measurements in even-parity Rydberg series of PbIusing 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.

Violet Diode Laser in Time-Resolved Stored-Ion Spectroscopy

Lifetime measurements of the metastable 3d D-2(3/2) level in singly charged calcium were performed using the newly developed violet diode laser operated in an external cavity arrangement. The laser was employed on stored ions at the CRYRING facility to optically pump the resonance line at 397 nm. In combination with laser probing at 866 nm this detection scheme gave the possibility to record the lifetime of this level. which has a radiative lifetime of about 1 s.