Pulsing and Continuous Wave

The timing of the emission is clearly dependent on the system in use. For example, if pumping is relatively slow and stimulated emission is fast, then the emergent beam of laser light will appear as a short pulse (subsequent lasing must await sufficient population inversion). This behavior is 

Interaction of an excited-state atom (A ) with a photon stimulates the emission of another photon so that two coherent photons leave the interaction site. Each of these two photons interacts with two other excited-state molecules and stimulates emission of two more photons, giving four photons in ail. A cascade builds, amplifying the first event. Within a few nanoseconds, a laser beam develops. Note that the cascade is unusual in that all of the photons travel coherently in the same direction consequently, very small divergence from parallelism is found in laser beams. 

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Bowman M K 1990 Fourier transform electron spin resonance Modern Pulsed and Continuous-Wave Electron Spin Resonance ed L Kevan and M Bowman (New York Wiley) ch 1, pp 1—42... 

L. Kevan and M.K. Bowman (Eds.), Modern Pulsed and Continuous-Wave Electron Spin Resonance, Wiley, New York, NY, 1990. 

Kevan, L. and Bowman, M. K. (1990) Modern pulsed and continuous-wave EPR spectroscopy. Wiley, New York. 

Karu TI, Tiphlova OA, Matveyets YA, Yartsev AP, Letokhov VS. Comparison of the effects of visible femtosecond laser pulses and continuous wave laser radiation of low average intensity on the clonogenicity of Escherichia coli. J Photochem Photobiol B Biol 1991 10 339. 

L Kevan, M K Bowman, Modem Pulsed and Continuous-wave Electron Spin resonance, Wiley, New York, 1990... 

As noted earlier, NMR lines from solids are very broad, but as early as 1958 Raymond Andrew and Irving Lowe independently showed that rapid spinning of the sample under certain conditions can reduce the line width. During the period 1965—1975 a number of clever new methods were developed (primarily in the laboratories of John Waugh, Alex Pines, Peter Mansfield, and Robert Vaughn) to employ both pulsed and continuous wave NMR methods to obtain narrow lines in solids. We shall describe the basic ideas behind these techniques and give some illustrations of their application. 

H. Kurreck, B. Kirste, W. Lubitz, ENDOR Spectroscopy of Radicals in Solution, VCH, 1988 E. R. Davies, Phys. Lett. A 1974, 47, 1-2 Arthur Grupp and Michael Mehring, in Modem Pulsed and Continuous Wave ESR , 1979, 195-229. 

McLauchlan, K. A. In Modem Pulsed and Continuous-Wave Electron Spin Resonance-, Keva, L. Bowman, M. K., Eds. Wiley New York, 1990 pp. 285-363. 

Cimrova V, et al. 2002. Comparison of the birefringence in an azobenzene side chain copolymer induced by pulsed and continuous wave irradiation. Appl Phys Lett 81(7) 1228 1230. 

In the early 1980s, clinical echocardiography was performed with a sector scanner, a stand-alone Doppler unit capable of a pulsed and continuous-wave mode operation, a spectral analyser with high temporal resolution and an in-house black box which allowed EKG display along with the spectra (Gramiak and Holen 1984). Due to the fact that small gas bubbles dissolve rapidly in blood, the next aim was the production of agents small enough to traverse the pulmonary capillary bed. 

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