Molecules high-power lasers

Thus, fluorescence may occur in aminoazobenzene-type compounds, but it is not prominent. Low-temperature, glassy solvents or other methods of external rigidification, such as adsorption to a surface at liquid nitrogen temperature, are necessary. For 4-dimethylaminoazobenzene, fluorescence in hydrocarbon solution at 77 K is on the red side of the n —> 7i band and assigned to n<—7t emission. With the high-power lasers available today, one would anticipate emission of many molecules of this class. 

Note With high-power lasers, simultaneous absorption of two or more photons by a molecule may lead to emission of a single photon with a greater frequency than that of the individual photons absorbed.]... 

In 1985 chemists at Rice University in Texas used a high-powered laser to vaporize graphite in an effort to create unusual molecules believed to exist in interstellar space. Mass spectrometry revealed that one of the products was an unknown species with the formula Ceo- Because of its size and the fact that it is pure carbon, this molecule has an exotic shape, which the researchers worked out using paper, scissors, and tape. Subsequent spectroscopic and X-ray measurements confirmed that Ceo is shaped like a hollow sphere with a carbon atom at each of the 60 vertices. Geometrically, buckyball (short for buckminsterfullerene ) is the most symmetrical molecule known. In spite of its unique features, however, its bonding scheme is straightforward. Each carbon is xp -hybridized, and there are extensive delocalized molecular orbitals over the entire structure. 

Another potentially important area of applications in opto-electronics is in the production of non-linear optical (NLO) devices. In section 9.2.1 the molecular electrical polarisability a is defined, with the assumption that the polarisation of a molecule is proportional to, or linear in, the applied electric field E. For sufficiently high electric fields, such as those that can be produced in high-power laser beams, the polarisation is no longer linear in E, but depends also on higher powers of E. This leads to various possible effects, some of which are now described. 

The third section is the chamber in which a high power laser ablates the particles and ionizes the atoms and molecules that are produced. Finally, in the fourth section, which is maintained at high vacuum, the positive and negative ions formed in the ablation/ ionization process are analysed using dual TOF mass spectrometers. 

---