A portable fibre-probe fluorescence detection system comprising a continuous-wave high-power ultraviolet light emitting diode (UV LED) emitting at 365 nm as excitation source, a bifurcated fibre probe with a six-around-one fibre configuration to illuminate and read from a large target area (∼3.6 mm2) and an integrated PC-coupled spectrometer has been developed. The construction, calibration and operation of the fluorescence detection system are described. Demonstrative test measurements with the system for possible inspection of different ripening stages on some batches of horticultural and agricultural products (lemon, mandarin, banana leaf and ivy leaf) have been performed and results presented. The system is portable, comparatively low cost, easily operated and relative immune to ambient light, thus being suitable for field measurements.

Twenty nine rovibronic lines of 12 C 17 O for which laboratory wavelengths were previously unavailable were detected in laser-induced fluorescence excitation spectra of the six vibronic bands A 1 Å( 0 ¼ 0Y5)YX 1 AE þ ( 00 ¼ 0). Rovibronic lines of 12 C 16 O, 13 C 16 O, 12 C 17 O, and 12 C 18 O were detected in each band, allowing accurate determination of the unknown wavelengths using neighboring 12 C 16 O and 13 C 16 O lines as reference. The new wavelength data yield consistent heliocentric velocity values when applied to vacuum ultraviolet observations of 12 C 17 O and 12 C 18 O in the interstellar medium.

The four carbon monoxide (CO) isotopomers 12 C 16 O, 13 C 16 O, 12 C 18 O and 12 C 17 O have been detected simultaneously in a CO gas sample of natural isotopic abundance by measuring rovibronic excitation spectra of six vibronic bands in the Fourth Positive System. The CO sample was flow cooled by adiabatic expansion in a pulsed supersonic jet. The rovibronic excitation spectra were obtained using a novel pulsed laser source (pulse duration $25 ns, spectral bandwidth $5 GHz) continuously tunable in the 139-155 nm vacuum ultraviolet wavelength region for excitation and recording the total fluorescence. In the present paper we report on the spectroscopic results obtained, including transition wavelengths of three forbidden rovibronic bands (e 3 R À À X 1 R + (1, 0), d 3 D À X 1 R + (5, 0), a 03 R + À X 1 R + (14, 0)) of 12 C 16 O and band origins of six rovibronic bands (A 1 P(v 0 = 0-5) À X 1 R + (v 00 = 0)) of the rare isotopomer 12 C 17 O, and on the experimental conditions facilitating the high sensitivity of the measurements. The exceptional sensitivity demonstrated by the results has been achieved by fine tuning experimental conditions including the conditions in the supersonic expansion, the jet pulse duration and the laser pulse timing.

For safety reasons, the need of a fast in situ technique for measuring change in surface hardness of nuclear reactor vessel walls due to ion bombardment has great importance. Material hardness measurement using laser induced breakdown spectroscopy has been demonstrated as a new promising technique. The effect of the material matrix is one of the challenges that this technique for hardness measurement may face. In this work, the plasma excitation temperature Te has been used to measure the relative hardness of some pure Ti and Ti alloy samples with different hardnesses. The hardness of these samples was changed by irradiating the samples with 1 MeV carbon (C) ions with different doses. On studying the average crystallite size of these samples using x-ray diffraction and its relation with hardness, it was found that pure Ti samples and Ti alloys show different behaviors. On the other hand, it was found that although there is a good linear relation between Te and the Vickers hardness, the sample matrices have a strong influence on the measurements, especially for samples with small hardness value differences, irrespective of their average crystallite size.

No abstract