Abstract: A method of determining surface plasmon resonances at two-dimensional measurement surfaces, in which the measurement surface which is formed by a thin metal film and which is brought into contact with a specimen to be measured is illuminated and the intensity distribution in the reflected beam is measured is to be further developed in such a way that it is substantially more sensitive (in respect of measurement) and is more resistant to interference. That is achieved in that the measurement surface is illuminated with two collimated monochromatic laser beams of differing wavelengths which are spatially combined to form an overall beam and the difference in the intensities reflected at the two wavelengths is measured to characterise plasma resonance.

Abstract: Described are a process and an apparatus for the remote measurement of uranium or plutonium in radioactive materials. in which the sample of the material to be analyzed is to be handled as little as possible. To attain that object it is proposed that the laser beam of a laser is focussed by means of a focussing unit onto the sample to be analyzed, so that a light-emitting plasma is generated, an image of the emission spectrum of the plasma is formed in a spectrograph by means of an imaging unit, and finally it is analyzed by means of an analyzing unit.

Abstract: Described are a process and an apparatus for the remote measurement of uranium or plutonium in radioactive materials, in which the sample of the material to be analyzed is to be handled as little as possible. To attain that object it is proposed that the laser beam of a laser is focused by means of a focusing unit onto the sample to be analyzed, so that a light-emitting plasma is generated, an image of the emission spectrum of the plasma is formed in a spectrograph by means of an imaging unit, and finally it is analyzed by means of an analyzing unit.

Abstract: Described are a process and an apparatus for the remote measurement of uranium or plutonium in radioactive materials, in which the sample of the material to be analyzed is to be handled as little as possible. To attain that object it is proposed that the laser beam of a laser is focussed by means of a focussing unit onto the sample to be analyzed, so that a light-emitting plasma is generated, an image of the emission spectrum of the plasma is formed in a spectrograph by means of an imaging unit, and finally it is analyzed by means of an analyzing unit.

Abstract: To improve the signal-to-noise ratio in trace analysis in gases or plasmas (3) by absorption spectroscopy the wavelength of the analyzing beam of a semiconductor laser (1) is modulated by a frequency f.sub.1 and the absorption length or population density of absorbing particles of the plasma is modulated by a frequency f.sub.2. For the measurement a lock-in amplifier (5) coupled to a photodiode (4) is tuned to the sum or difference frequency of the frequencies f.sub.1 and f.sub.2 or whole-number multiples thereof.