K Fredriksson

Mobile remote sensing system for atmospheric monitoring

A mobile optical remote sensing system for environmental monitoring is described. The system, housed in a full-size truck with a laboratory floor surface of 6.0 × 2.3 m2, is mainly intended for differential absorption lidar (DIAL) applications but can also be used for laser-induced fluorescence monitoring and for absorption measurements using classical light sources. The system has a 40-cm diam receiving telescope and a fully steerable flat mirror in a transmitting/receiving dome. A Nd:YAG-pumped dye laser with auxiliary nonlinear frequency conversion is the preferred transmitter in DIAL measurements. Measurement examples for atmospheric SO2 and NO2 monitoring with automatic concentration map drawings are given and further uses are discussed.

Mobile lidar system for environmental probing

A fully mobile remote-sensing system based on the lidar principle is described. With this system, atmospheric probing using Mie scattering, differential absorption, or Raman techniques can be performed yielding information on atmospheric pollutants or general atmospheric parameters. The system incorporates a powerful Nd:YAG laser pumping a dye laser and is equipped with a fixed Newtonian telescope used in conjunction with a flat steering mirror. The lidar signals are electrically recorded using a fast-transient digitizer and are processed by a minicomputer, which also controls the laser, the chosen measuring direction, and the output media. Examples of measurements on atmospheric NO(2) and SO(2) are given.

Evaluation of the DIAL technique for studies on NO2 using a mobile lidar system.

The DIAL technique for remote monitoring of nitrogen dioxide is evaluated. A comprehensive field test and evaluation program was performed to determine the measuring capability for this pollutant. The potential sources of error are discussed and these are analyzed for the mobile lidar system used in the work. This system employs a dye laser pumped by a Nd:YAG laser; a laser source which has improved the measuring accuracy compared with earlier work on nitrogen dioxide. The accuracies are found to be good enough for measuring needs in many studies on air pollution problems. A few typical examples of measurements from the field test program are given.

Lidar system applied in atmospheric pollution monitoring

A lidar system, incorporating tunable dye lasers and a 25-cm diam Newtonian telescope, has been constructed and applied in atmospheric pollution monitoring. The system, which is fully controlled by a specially designed microcomputer, has been used in several field tests, where stack effluents as well as the ambient air have been monitored. Results from particle, NO(2), and SO(2) measurements are discussed.

DIAL techniques for the control of sulfur dioxide emissions.

An extensive program for the evaluation of the DIAL (differential absorption lidar) technique was performed. Measuring and evaluation routines for DIAL measurements on sulfur dioxide in different applications were made. Several field tests were performed with a mobile lidar system employing a Nd:YAG laser pumping a dye laser. Examples of measurements from the work are given. The practical aspects of the technique and the field of applications are discussed.

DIAL technique for pollution monitoring: improvements and complementary systems.

Improvements to and complementary systems for a differential absorption lidar system for field work are discussed. A dual-wavelength laser and a dual-wavelength detection system, which make DIAL with simultaneous lidar measurements at two wavelengths possible, are described. A multiwavelength measurement routine, which will improve accuracy and detection limits, is proposed. A dual-beam lidar system for measurements of plume velocity is also described.

Stark interaction for excited states in alkali atoms, investigated by laser spectroscopy

The scalar polarizability constantα0 for excitedS- andD-states in rubidium and cesium was measured utilizing a two-step excitation scheme. An rf lamp and a single-mode dye laser were used to excite the atoms in a collimated atomic beam. Values ofα0 were determined for the 9–102S1/2 and 7–82D3/2 states of rubidium and for the 10–132S1/2, 9–102D3/2 and 9–112D5/2 states of cesium. Further, the isotope shift was evaluated in the 5579 Å rubidium line. A review of experimental polarizability constants for rubidium and cesium is given, and the results are compared with theoretical values.

Investigation of the fine structure in the 2 D sequence of sodium using level-crossing spectroscopy

Splittings in the n 2 D sequence were measured for n=4-9. An accuracy of about 0.1% was obtained in level-crossing measurements on an atomic beam. The D states were populated by step-wise excitation, using an RF lamp and a CW dye laser. A method for measuring the sign of the spin-orbit coupling constant is demonstrated. With the present measurements, the highly anomalous n 2 D sequence in sodium has now been studied for n=3-16.

Measurement of the fine-structure splitting of the 42D state of lithium using level-crossing spectroscopy

The fine-structure splitting of the 42D state in lithium was measured using stepwise laser excitation combined with level-crossing spectroscopy. The splitting was determined to be 456.2(0.8) MHz, a considerably higher value than the one obtained in a recent level-anticrossing measurement. The new value is in good agreement with the result of a Hartree-Fock calculation, 460.2 MHz.

Fine-structure measurements for highly excited F states of cesium

The fine-structure splittings of highly excited F-states in Cs were measured using high-resolution laser spectroscopy. The 12 and 132F states were found to be inverted with splittings ΔE (122F)=−522(3) MHz and ΔE (132F)=−416(3) MHz.