K S Bhatia

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.

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.

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.

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.

Ionization of high Rydberg states of calcium by electric fields

Abstract Measurements of electric field ionization of high Rydberg states populated by two-photon excitation are reported. We use a novel technique, in which the extraneous ionization background due to other causes is suppressed, resulting in higher accuracy and sensitivity than otherwise achievable. The method is applied to a series in the calcium spectrum which exhibits an interesting anomaly around n = 63 in previous experiments by laser spectroscopy using thermionic diode detection. In the present experiments, collisions are highly improbable, and it is demonstrated that electric field ionization then occurs without any detectable anomaly around n = 63. The implications of this for the interpretation of the effect are discussed.