Time-resolved photon counting with digital oscilloscope

Abstract. Photon counting by means of a digital oscilloscope controlled by a computer is presented. For many applications this system can replace commercially available gated or multichannel photon counters

SAWA experiment ? properties of mineral dust aerosol as seen by synergic lidar and sun-photometer measurements

International audienceWe propose a method of retrieving basic information on mineral dust aerosol particles from synergic sun-photometer and multi-wavelength lidar measurements as well as from the observations of lidar light depolarisation. We use this method in a case study of mineral dust episode in Central Europe. Lidar signals are inversed with a modified Klett-Fernald algorithm. Aerosol optical depth measured with the sun-photometer allows to reduce uncertainties in the inversion procedure through which we estimate vertical profile of aerosol extinction. Next we assume that aerosol particles may be represented by ensemble of randomly oriented, identical spheroids. Having calculated vertical profiles of aerosol extinction coefficients for lidar wavelengths, we compute the profiles of local Angstrom exponent. We use laser beam depolarisation together with the calculated Angstrom exponents to estimate the shapes (aspect ratios) and sizes of the spheroids. Numerical calculations are performed with the transition matrix (T-matrix) algorithm by M. Mishchenko. The proposed method was first used during SAWA measurement campaign in Warsaw, spring 2005, to characterise the particles of desert dust, drifting over Poland with a southern-eastern wind (13?14 April). Observations and T-matrix calculations show that mode radii of spheroids representative for desert aerosols' particles are in the range of 0.15?0.3 ?m, while their aspect ratios are lower than 0.7 or larger than 1.7

Observation of ozone concentration during the solar eclipse

Abstract We report the results of measurements of ozone concentrations during the solar eclipse of 11 Ž . August 1999. The experiment was performed in Warsaw Poland and its surroundings. The temporal evolution of ozone concentration was measured using the differential absorption lidar Ž . DIAL and it was compared with results obtained by several monitoring stations measuring with other methods. In almost all cases, a drop in the ozone concentration was observed during the eclipse. Experimental data was compared with calculations done using a simple model based on NO -O chemical kinetics. q 2001 Elsevier Science B.V. All rights reserved

Laser spectroscopy for breath analysis : towards clinical implementation

Detection and analysis of volatile compounds in exhaled breath represents an attractive tool for monitoring the metabolic status of a patient and disease diagnosis, since it is non-invasive and fast. Numerous studies have already demonstrated the benefit of breath analysis in clinical settings/applications and encouraged multidisciplinary research to reveal new insights regarding the origins, pathways, and pathophysiological roles of breath components. Many breath analysis methods are currently available to help explore these directions, ranging from mass spectrometry to laser-based spectroscopy and sensor arrays. This review presents an update of the current status of optical methods, using near and mid-infrared sources, for clinical breath gas analysis over the last decade and describes recent technological developments and their applications. The review includes: tunable diode laser absorption spectroscopy, cavity ring-down spectroscopy, integrated cavity output spectroscopy, cavity-enhanced absorption spectroscopy, photoacoustic spectroscopy, quartz-enhanced photoacoustic spectroscopy, and optical frequency comb spectroscopy. A SWOT analysis (strengths, weaknesses, opportunities, and threats) is presented that describes the laser-based techniques within the clinical framework of breath research and their appealing features for clinical use.Peer reviewe

Investigations of Electron Impact Induced Excitations from 3P to Higher Lying Levels of Sodium

Results of measurements of the rate constants for the electron impact induced transitions between 3P and higher excited 3D, 4P, and 5S levels are presented. The experimental data were corrected for the radiation imprisonment using a new model of this effect

Investigation of Collisions between Li(2P) Atoms and Electrons: Excitation of 4l Levels

Results of measurements of rate constants for transitions between 2P → 4S, 2 P → 4P, and 2P → 4D levels of lithium are presented. The investigations were performed in laser induced plasma. The results were compared with calculations based on Born and close coupling approach

Investigation of Radiation Trapping in Atomic Vapour Excited by Weak Resonant Laser Pulses

We present results of our investigations on radiation trapping in sodium vapour excited to 3P level by weak laser pulses. The evolution of the fluorescence signal as well as the evolution of excited atoms distribution were studied using the Monte Carlo method. Some predictions of these investigations were checked experimentally

Investigation of Collisions between Li(2P) Atoms and Electrons: Excitation of 4l Levels

Results of measurements of rate constants for transitions between 2P → 4S, 2 P → 4P, and 2P → 4D levels of lithium are presented. The investigations were performed in laser induced plasma. The results were compared with calculations based on Born and close coupling approach