Ambient fi elds generated by a laser

An optical breakdown caused by a nanosecond laser beam focused into a gaseous medium forms a laser spark in the given gaseous environment. The most likely processes triggered by the spark are those of radiation chemistry forming radicals and more complex molecules from originally simple gas components. Owing to its high energy density, the laser spark is an ideal instrument to simulate the energetic events in the planetary atmospheres, such as meteorite impacts. The spark, however, generates not only the radiation, but also ambient macroscopic electric and magnetic fi elds, which may infl uence the outcome of the mentioned radiation synthesis. The most striking example is sometimes the absence racemization of optically active products (enantiomeric imbalance), i.e. a surplus of one kind of optical isomer. This concerns molecules like amino acids [1, 2], which are thought later to have participated in more complex organic syntheses leading to the origin of terrestrial life. A useful survey on laser plasma chemistry is to be found in [3]. Quite recently, experiments involving heterogeneous systems with the liquid formamide as a primitive compound have been arranged in a similar confi guration and it was found that all the four nucleobase constituents of RNA can be synthesized by a single laser shot, as shown in [4]. As mentioned above, some of the created molecules Ambient fi elds generated by a laser spark Karel Rohlena, Martin Mašek