Forbidden transition, 125 detectors

The allowed transition 6 5i/2-6 Pi/2 serves as an amplifying detector for a single quantum jump on the dipole-forbidden transition 5 Ds/2 6 5i/2 [1232]. In... 

And although om natural and personal detector, the retina, shows us a tranquil sky, with a light scatter of stars across it, striking only by its steadfast inaction, the new sky revealed by telescopes and satellites sensitive to invisible emissions is one of tempest. It is animated by the birth of clouds, the creative explosion of stars and the transition of the Universe from opacity to transparence. Human perception now contemplates regions once forbidden to it. 

Also crucial to our experiment were recent advances in the techniques of optical spectroscopy[13]. We combine the pulsed Ps source with a high power narrowband dye laser[23] capable of partially saturating the highly forbidden two photon 1S-2S transition over a sizable volume of space, the use of two-photon techniques[24] that allow us to avoid the considerable first order Doppler width and to excite all the Ps when the laser is tuned to the atomic resonance, and a single atom, resonant ionization detector [25] with a low background counting rate and 40% quantum efficiency. 

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