Progress in modern radio astronomy led to the discovery of space masers in the microwave range, and it became a powerful tool for studies of interstellar star-forming molecular clouds. Progress in observational astronomy, particularly with ground-based huge telescopes and the space-based Hubble Space Telescope, has led to recent discoveries of space lasers in the optical range. These operate in gas condensations in the vicinity of the mysterious star Eta Carinae (one of the most luminous and massive stars of our Galaxy). Both maser and laser effects, first demonstrated under laboratory...

Prefaces are usually written when a manuscript is finished. Having finished this book I can clearly see many shortcomings in it. But if I began to eliminate them I would probably write quite a different book in another two years; indeed, this has already happened once. In 1979, when I finished the first version of this book, it was much broader in scope and was to be titled "Laser Photochemistry." Corrections and additions to that unpublished manuscript gave rise to the present book with its revised title and more specific subject matter. I resolved to have it published in exactly this form,...

The laser as a source of coherent optical radiation has made it possible to investigate nonlinear interaction of optical radiation with atoms and mole cules. Its availability has given rise to new research fields, such as non linear optics, laser spectroscopy, laser photochemistry, that lie at the boundary between quantum electronics and physical optics, optical spectros copy and photochemistry, respectively. The use of coherent optical radiation in each of these fields has led to the discovery of qualitatively ne effects and possibilities; in particular, some rather subtle effects of...