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Super-Resolution Fluorescence Techniques
Published in Bethe A. Scalettar, James R. Abney, Cyan Cowap, Introductory Biomedical Imaging, 2022
Bethe A. Scalettar, James R. Abney, Cyan Cowap
Stimulated absorption is the excitation process that we encountered in Chapters 6 and 7; it occurs when a molecule in a low-energy state is stimulated into a higher energy state by absorption of a photon with energy matched to the difference in energy between the two states (Eq. [7.6] and Fig. 8.9). Spontaneous emission (e.g., fluorescence) similarly is the radiative follow-up that we encountered in Chapters 6 and 7. Spontaneous emission occurs when the excited molecule releases its energy without any outside stimulation. Each type of fluorophore has a characteristic spontaneous emission time, which is known as the fluorescence lifetime. Fluorescence lifetimes are on the order of nanoseconds and represent the average time spent in the excited state before spontaneous release of a photon (HW 8.8).
Properties of Participating Media
Published in John R. Howell, M. Pinar Mengüç, Kyle Daun, Robert Siegel, Thermal Radiation Heat Transfer, 2020
John R. Howell, M. Pinar Mengüç, Kyle Daun, Robert Siegel
Equation (1.46) gives the attenuation of intensity passing through an absorbing, nonemitting, non-scattering medium as would be observed by detectors of the incident and emerging radiation. Such information could be used in determining κλ. Actually, as radiative energy passes through a translucent medium, not only is it absorbed, but there is an additional phenomenon where the radiation field stimulates some of the atoms or molecules to emit energy. This is not ordinary or spontaneous emission caused by the temperature of the medium, as discussed in Section 1.9.4. The spontaneous emission is the result of an excited energy state of the medium being unstable and decaying spontaneously to a lower energy state. Emission resulting from the presence of the radiation field is termed stimulated or induced emission and acts like negative absorption.
Self-Assembled Nanoparticle Optical Antennas
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
Kateryna Trofymchuk, Guillermo P. Acuna, Viktorija Glembockyte, Philip Tinnefeld
Spontaneous emission is a relaxation process of an emitter from an excited state (S1) to a state with lower energy (usually the ground state, S0) that is accompanied by a single photon radiation. Although for a long time spontaneous emission rate of emitters was considered as an inherent and unchangeable property, now it is known that it depends on the EM environment around the emitter (Purcell, 1946; Drexhage, 1970). Being a microscopic process, spontaneous emission still requires a quantum mechanics treatment. Its corresponding radiative rate kr could be described by Fermi’s “golden rule” (Eq. 8.1): kr=[⟨i|H|f⟩2ℏ]p(v)
Spontaneous emission from nonhermitian perspective: complex scaling of the photon coordinates
Published in Molecular Physics, 2019
Spontaneous emission (SE) is usually understood as a dissipative process, in which an atomic/molecular system (prepared initially in an excited electronic state) releases its energy in the form of outgoing photons. Emission of photons occurs here due to a weak coupling between the atom/molecule and all the modes of the quantum electromagnetic field [1–4]. Due to such a coupling, an initially prepared excited atomic/molecular state becomes metastable, i.e. possesses a finite decay rate which is conventionally determined by means of the Golden Rule formula [4].
Percutaneous laser ablation of cervical metastatic lymph nodes in papillary thyroid carcinoma: clinical efficacy and anatomical considerations
Published in Expert Review of Medical Devices, 2021
Eleftherios Spartalis, Sotirios P. Karagiannis, Nikolaos Plakopitis, Maria Anna Theodori, Dimitrios I. Athanasiadis, Dimitrios Schizas, Michael Spartalis, Theodore Troupis
Laser is an acronym for ‘light amplification by stimulated emission of radiation’ [7]. Laser light is produced from the spontaneous emission of characteristic photons by excited atoms and enables the precise transmission of significant amounts of energy from a source to small well-defined areas over a long distance [7,11]. It is delivered to the patient via an optic fiber directly inserted into the target organ [7].