Photonics response

The two parts of this formula are derived from the same QED Feynman diagram for interaction of two electrons in the Coulomb gauge. The first term is the Coulomb potential and the second part, the Breit interaction, represents the mutual energy of the electron currents on the assumption that the virtual photon responsible for the interaction has a wavelength long compared with system dimensions. The DCB hamiltonian reduces to the complete standard Breit-Pauli Hamiltonian [9, 21.1], including all the relativistic and spin-dependent correction terms, when the electrons move nonrelativistically. 

The slow-scan CCD, also called the scientific CCD, or in the spectroscopy literature simply CCD, is the detector of choice for most applications of Raman spectroscopy. A well-designed CCD has essentially zero dark current, very low readout noise, and high quantum efficiency (peak 45—70% near 700 nm) in the visible region of the spectrum. However, the response drops quickly above 800 nm and there is no photon response above 1.05 J m. For routine spectroscopy or process control, thermoelectrically cooled (to about —40° C) CCDs are adequate. Although these detectors are somewhat noisier than detectors operated at —100° C or lower, the former do not require liquid nitrogen cooling. The general properties and spectroscopic applications of the CCD have been reviewed (22). 

Fig. 10. Single-photon response of a RCA 8850 photomultiplier demonstrating the principle of two-channel sampled timing. In all three cases, the channel 1 sampled voltage exceeds the lower level discriminator. In the top example, the channel 2 sample is nearly equal and is accepted. In the other two examples, the current pulses arrive 1 ns late and 1 ns early and the large differences between the two sampled voltages causes these photons to be rejected. (After ref. 57.)...

In cells, improved timing accuracy arises from cascades of phosphorylation events. This insight is in fact the theoretical basis for a recent kinetic model for phototransduction signaling in vertebrate rod cells published by Hamer et al. [76]. It is proposed that multiple, successive phosphorylations of rhodopsin by rhodopsin kinase lead to high accuracy in the single-photon responses of a rod cell. Briefly, if we assume n identical, irreversible phosphorylation steps with only the fully... 

R. D. Hamer, S. C. Nicholas, D. Tranchina, P. A. Liebman, and T. D. Lamb. Multiple steps of phosphorylation of activated rhodopsin can account for the reproducibility of vertebrate rod single-photon responses. J. Gen. Physiol., 122 419 144,... 

Photon responses from sample-ultrasonic (or hypersonic) interaction... 

Fig. 1.4 Single photon response (left) and transit-time distribution (right) of a Hamamatsu R3809U MCP, from [211]...

Exploitation of photons by supramolecular systems for information purposes can be performed by two different routes (Scheme I). The first one ("photon-writes"), involves the occurrence of a photorcaction in a supramolecular species that causes ("writes") some changes in the properties of the species, reflected in a monitorable signal. The second route ("photon-reads") is based on a some kind of interaction between components of a supramolecular system and an external species which affects the photon response of the system. Some excited state manifestation (most usually, luminescence) can therefore be used "to read" the interaction. 

Novel Photonic Responses from Low-dimensional Crystals of Thiophene/Phenylene Oligomers... 

Colour perception in humans is initiated by the absorption of light by three different spectral classes of cone cells present in the retina, conveniently referred to as blue, green and red. Each class exhibits a different but overlapping spectral sensitivity, with maximum values at ca. 419, 531 and 558 nm respectively. The sum of the differing sensitivities is called the photonic response and displays a maximum value at 555 nm. However colour perception can be very subjective, and the description of colour differences can be quite challenging. Colorimetry and the trichromatic perception of colour are based on Grassmans laws [19, 20] ... 

Ketter JK, Forty SP, Wightman RM, Eeldberg SW (2004) Use of DigiSim to model cyclic voltammetric and photonic responses in electrogenerated chemiluminescent systems. Electrochem Solid-State Lett 7 E18-E22... 

According to a review on Kerr-like optical nonlinearities in liquid crystal [149], these experiments show that the photonic response may be much faster if short intense laser pulses are used instead of low-power cw laser radiation. This may open new aspects and perspectives in research and applications. In [150], the necessary conditions for the observation of resonance non-linearities in dye-doped CLCs are summarized ... 

Nanoparticles can be ordered at the detector surface or elsewhere using self-assembly techniques or pattering by top-down approach. They can be distributed in regular patterns, thus accurately controlling the interparticle distance or they can be randomly scattered. A possible way to implement nanoparticles for plasmonic enhancement is to arrange them in a quasicrystal pattern (for instance Penrose tiling), which ensures an isotropic photonic response of the strucmre [325]. 

Tests of a small pad chamber with vacuum-deposited Csl or CsI-f-TMAE reflective cathodes have confirmed the expected fast and stable single photon response, but tlie quantum efficiency was only about 50% of the expected value. This loss is attributed to long air exposure of the < athode pads while the wires were being strung. Chambers with reflective solid jihotocathodes developed for the Fast RICH prototype are designed to allow fast chamber assembly with minimum air exposure of the cathode. Beam tests of these chambers is expected to begin in fall 1993 [13]. 

Arshavsky, V.Y., Rhodopsin phosphorylation from terminating single photon responses to photoreceptor dark adaptation, Trends Neurosci., 25, 124, 2002. 

To experimentally investigate TPA focal spots, one needs a direct two-photon responsive medium. When IR ultrashort laser pulses were tightly focused in a resin, initiators were decomposed into radicals by simultaneously absorbing two photons. The number of photons absorbed per molecule per unit time by means of TPA is proportional to the TPA cross-section, dand to SLI. The total number of photons absorbed per unit time is also a function of initiator concentration, C, and the excited sample volume, V. In the absence of saturation and photobleaching, the number of radicals generated per unit time, AT, is given by ... 

Fig. 3. Photon response of non-AR coated EBC detector eddbits nearly flat response over wide waveband ( 8-25pm).

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