Y. Makdisi

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.

Accurate method for the determination of the refractive index of liquids using a laser

Refractive indices of water and several organic liquids have been determined by an accurate method using a He‐Ne laser. The method is in principle simpler than those used normally for such measurements. The experimental arrangement presented here is capable of yielding results with an accuracy of the order of 2×10−5. Comparison between the measured values and precise published results shows that they are nearly same within experimental parameters.

Absorption spectrum of Sb I by a flash pyrolysis technique

The absorption spectrum of neutral antimony vapours has been photographed in the spectral range 1425-2530 AA with a 3 m normal incidence vacuum spectrograph using a flash pyrolysis technique. Over 400 spectral lines have been classified as a combination between 5 odd parity levels of the ground-state configuration and 141 even parity levels. One long and four short series of the 5s25p2(3P0,1,2)ns configurations are listed. Fifty-eight new levels have been added to the previous analysis.

New study of the even-parity spectrum of Ca I and of the influence of collisions on high Rydberg states

A new study of the even-parity spectrum of Ca I is reported. The term assignments of the 3d2 doubly excited configuration are discussed in relation to those of the isoelectronic sequence and to the corresponding assignments in Ti I. The significance of term-dependent contraction of the 3d orbitals in Ca I, not considered in earlier studies of this spectrum, is demonstrated from ab initio Hartree-Fock calculations, and the energies of the missing terms are estimated. The authors show that data for the members n=62 to 85 of 4snd 1D2 do not agree as well as originally surmised with earlier MQDT extrapolations, indicating the presence of a further perturbation. They have investigated the breakdown of the Delta J selection rule in the presence of collisions with a foreign gas. A collision-induced perturbation around n=63 of 4snd 1D2 is used to locate the missing 1G4 term of 3d2.

Laser refractometry of liquids with a diffraction grating

Abstract A technique is described in which the measurement of the wavelength of a laser beam travelling through a liquid provides a quick and accurate method of determining the refractive index of the liquid. The operation principle of the technique, which is based on the diffraction of light, is outlined. Measurements have been carried out on water and several organic liquids with considerable accuracy. Uncertainties in results are found to be less than 0.03%. Refractive indices determined by this method are in good agreement with literature values.

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.

Laser and Thermal Annealing Effects on the Optical Properties of n-GaAs [100] Crystals: Application to Its Schottky Diodes

Measurements of optical absorption, reflectance and transmittance properties have been made experimentally on [100] n-GaAs crystals to study the effects of laser and thermal annealings on these materials. Experimental evidence of the deterioration of the absorption coefficient a has been observed as a function of the photon energy for different laser power densities: 12, 24, 36 and 48 mW/cm 2 and for different thermal annealing temperatures in the ranges: 77 K and 20 to 200 °C. The influence of these effects has been observed in the characteristics of GaAs Schottky diode as well.

Gallbladder stone inspection and identification for laser lithotripsy

Using high speed imaging techniques, the gall bladder stone immersed in liquid is detected and identified. The detection of the shock waves induced by laser power is reached by using interferometry technique. Using gall bladder and tissue images obtained by ultra-fast photography and time resolved laser fluorescence the correlation of correlation is performed. The tissue image is used to perform the correlation filter. Hence lower correlation output is used for firing of the laser power.

Spectral line broadening of Sr under the influence of collisions with foreign gas perturbers

Abstract The collision broadening of strontium Rydberg states under the influence of Xe, Ar and He gases has been studied by laser spectroscopy of two-photon excitation of Sr in a heat pipe. Broadening data for the 5snd 1D2 series are reported with buffer gas pressure in the range of 10 Torr to 500 Torr. Observed anomalies in broadening parameters due to inter-configuration perturbation are discussed.

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.