M Marafi

Measurement of fluorescence decay of crude oil: A potential technique to identify oil slicks

The single photon counting technique has been used to measure the decay time for several Kuwaiti crude and refined oils. Fluorescent characteristics of two different bunker oils from widely separate geographic areas have been studied. Laser induced fluorescent data for the crude oil samples are compared with the decay time results to evaluate the potential of these techniques for the identification of oil sticks in the marine environment. Response of the oil film thickness to various excitation wavelengths from a CW Ar ion laser and a pulsed xenon lamp has been investigated.

Collisional shifts and broadenings of doubly excited states of barium

Shift and broadening parameters for doubly excited states of 5d6d, 5d7d, 5d7s, 5d8s and 6p2 configurations in neutral barium atoms are presented. A tunable dye laser pumped by an excimer laser was used to populate the Rydberg states of Ba by two-photon absorption from the 6s2 1S0 ground state. Inert gases Ar, Kr and Xe at 100 mbar pressure were used as perturbing gases. The resulting line shapes were fitted to a Voigt line shape function, from which shift and broadening parameters were inferred.

Collisional shifts and broadenings of the 4sns 1S0 and 4snd 1D2 Rydberg series of calcium perturbed by inert gases

An excimer pumped dye laser was used to measure collisional shift and broadening rates of the nd 1D2 (n = 4–50) and ns 1S0 series (n = 5–30) of calcium Rydberg states. Two-photon absorption techniques were used to populate the Rydberg states. High-resolution Ca excitation spectra were measured using a diode detector while scanning the frequency of the dye laser. Inert gases Ar, Kr and Xe were used as perturbers at pressures of 100 mbar. Shifts and broadenings of spectral lines were measured as functions of the principal quantum number n. The pressure-dependence behaviour of the 4s63d 1D2 Rydberg state as well as its configuration interactions is discussed.

Shifts and broadenings of barium Rydberg states perturbed by inert gases

Collisional broadening and shift data for even parity states of neutral barium are presented. A two-photon absorption technique is used to populate Rydberg states of nd 1D2, 3D2 and 1S0 series. High-resolution Ba excitation spectra were measured using a diode detector while scanning the frequency of an excimer pumped dye laser. Inert gases Ar, Kr and Xe were used as perturbers at pressures ranging from 10 mb to 400 mb. Shifts and broadenings of spectral lines were measured as a function of pressure and principal quantum number n. Several perturbations and deviations from expected results are discussed in this paper.

Collision-induced shifts of Rydberg levels of strontium

Measurements of spectral line shifts induced by collisions with rare gas perturbers are reported. High Rydberg states were prepared by multiphoton excitation using an excimer pumped tunable dye laser. A thermionic detector inside a heat pipe was used to collect the ionization products resulting from excited states. Analysis of the data for the shifts of the absorption transition to 5snd 1D 2 states in strontium is presented.

Visualization of ultrafast phenomena during the laser-induced lithotripsy

Optical coherent techniques, inteferometry and microscopy are applied for visualization of phenomena associated with laser-based lithotripsy. Shadowgraphy and ballistic imaging is used to visualize the phenomena generated around a stone during the action of a laser pulse. Results are confirmed using optical and electron microscopy.

Correlation of the gallbladder stone and tissue fluorescent images

Fluorescent images of gallbladder stones, tissue and bile are obtained using a streak camera. A Match Spatial Filer (MSF) is made using a stone fluorescent image. The MSF is used to perform correlations with fluorescent tissue and bile image. A method for recognition of the stone and rejection of the tissue during the laser lithotripsy is proposed using the correlation outputs.