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Fluorescence spectroscopy is an analytical technique used to measure the fluorescence emitted by a substance after it has absorbed light or other electromagnetic radiation. This technique is based on the principle of fluorescence, where certain molecules (fluorophores) absorb light at a specific wavelength and subsequently emit light at a longer wavelength.

The term "forbidden mechanism" can have different meanings depending on the context in which it is used. Here are a few interpretations across different fields: 1. **Physics and Chemistry**: In these disciplines, a "forbidden mechanism" often refers to a reaction pathway or process that is not allowed under the laws of conservation or quantum mechanics. For example, in nuclear physics, certain decay processes may be classified as "forbidden" if they do not obey the selection rules governing allowed transitions.

Force spectroscopy is a technique used to study the mechanical properties of materials at the nanoscale by measuring the forces that arise during the interaction of a probe with a sample. It typically involves a sharp tip, often mounted on a cantilever, that interacts with a sample surface. The force exerted between the tip and the sample is measured as a function of distance, allowing researchers to obtain detailed information about the sample’s mechanical properties, such as elasticity, adhesion, and friction.

Fourier-transform spectroscopy (FTS) is an analytical technique used to obtain the spectrum of a substance by measuring the intensity of light as a function of wavelength or frequency. The core principle of FTS is the application of Fourier transform mathematics to process the data collected from spectroscopic measurements. Here’s how it works in a nutshell: 1. **Interferometry**: FTS typically employs an interferometer, such as a Michelson interferometer, to split an incoming light beam into two paths.

The Franck-Condon principle is a fundamental concept in molecular spectroscopy that pertains to the behavior of molecules during electronic transitions. It provides insight into why certain electronic transitions are favored over others in terms of their ability to absorb or emit light. The principle is based on the idea that during an electronic transition, such as the absorption or emission of a photon, the nuclei of the molecules do not have time to move significantly due to the very short timescales involved in electronic transitions.

A frequency comb is a tool used in physics and engineering that consists of a series of discrete, evenly spaced frequency lines or modes. It is typically generated by mode-locked lasers, which produce pulses of light at regular intervals. These pulses correspond to frequencies that are harmonically related, creating a "comb-like" spectrum of frequency lines when viewed in the frequency domain.

Functional magnetic resonance spectroscopy (fMRS) is a neuroimaging technique that combines elements of functional magnetic resonance imaging (fMRI) and magnetic resonance spectroscopy (MRS). While fMRI is primarily used to measure changes in blood flow and identify brain activity associated with various tasks or stimuli, MRS focuses on quantifying the concentration of specific metabolites in the brain.

The term "fundamental series" can refer to various concepts depending on the context in which it is used. Here are a few potential contexts: 1. **Mathematics**: In mathematics, particularly in the context of series and sequences, a "fundamental series" might refer to a series that serves as a basic or foundational example for studying properties of convergence, divergence, or other characteristics of series in analysis.

G-strain, often referred to in the context of aviation and high-acceleration environments, is a type of physical strain that results from exposure to gravitational forces (G-forces). When an individual experiences high G-forces, such as during rapid acceleration, sharp turns, or high-speed maneuvers, their body can undergo significant mechanical stress.

The GF method, or the Galerkin Finite Element method, is a numerical technique used for solving differential equations, particularly in the fields of engineering and applied mathematics. It is a type of finite element method (FEM) that combines the Galerkin method—which is a technique for converting a continuous problem (like a differential equation) into a discrete one—with the finite element analysis framework.

Gamma spectroscopy is an analytical technique used to measure and analyze the energy and intensity of gamma-ray radiation emitted by radioactive materials. This method is widely utilized in various fields, including nuclear physics, environmental monitoring, medical diagnostics, and radioactive waste management, among others. ### Key Concepts of Gamma Spectroscopy: 1. **Gamma Rays**: Gamma rays are high-energy electromagnetic radiation emitted during radioactive decay. They have no mass or charge, making them highly penetrating and difficult to shield.

Gas chromatography–vacuum ultraviolet spectroscopy (GC-VUV) is an analytical technique that combines gas chromatography (GC) with vacuum ultraviolet (VUV) spectroscopy to separate and identify chemical compounds in a sample. ### Key Components: 1. **Gas Chromatography (GC)**: This part of the technique is used for the separation of volatile compounds in a mixture.

Gas in the context of scattering media absorption spectroscopy refers to a state of matter in which particles, such as molecules or atoms, exist in a well-dispersed manner with relatively large spaces between them, allowing them to move freely. In spectroscopy, particularly absorption spectroscopy, gases can absorb specific wavelengths of light, leading to characteristic absorption spectra that can be used to identify and quantify the presence of certain substances.

"Globar" can refer to different concepts or entities depending on the context, but it is most commonly known as a type of thermal radiation source used in various scientific and industrial applications. 1. **Globar (Thermal Radiation Source)**: This is a silicon carbide rod that is heated to produce a broad spectrum of infrared radiation. It is often used in spectroscopic applications, such as Fourier-transform infrared spectroscopy (FTIR), where it serves as a stable and consistent source of infrared light.

Grating-coupled interferometry is a technique used in the field of optics and photonics to analyze the properties of light and its interactions with different materials. This method typically involves the use of a diffraction grating, which is an optical component with a periodic structure that disperses light into its component wavelengths. In grating-coupled interferometry, light is directed onto a grating, where it is diffracted into multiple orders of diffraction.

A Grotrian diagram is a visual representation used in spectroscopy and quantum mechanics to illustrate the energy levels of a particular atom or molecule and the transitions between them. It provides a graphical way to depict the electronic states of atoms and the allowed transitions (e.g., radiative transitions) that occur as electrons move between these states. In a Grotrian diagram: - **Energy Levels**: The vertical axis represents energy levels, where higher positions indicate higher energy states.

HITRAN, which stands for the High-resolution Transmission molecular absorption database, is a comprehensive database that contains information on the absorption and emission spectra of various molecules in the atmosphere. Developed primarily for use in atmospheric science and remote sensing, HITRAN provides data on the spectroscopic parameters of gases that are critical for interpreting and modeling the transmission of light in the atmosphere.

Heteronuclear single quantum coherence (HSQC) spectroscopy is a two-dimensional NMR (nuclear magnetic resonance) technique primarily used for the analysis of complex organic molecules, particularly those containing multiple types of nuclei, such as carbon-13 (\(^{13}C\)) and proton (\(^1H\)). The HSQC method allows for the correlation of these different nuclei, enabling chemists to better understand molecular structures and interactions.

The history of spectroscopy is a fascinating journey through science and technology that spans several centuries. Spectroscopy, the study of the interaction between matter and electromagnetic radiation, has roots in early optical experiments and has evolved into a key analytical technique across various scientific fields. ### Early Beginnings (17th - 19th Century) 1. **Isaac Newton (1671)**: The foundation of spectroscopy can be traced back to Newton's experiments with prisms.

Hund's cases refer to a classification system used in atomic physics and quantum mechanics to describe the coupling of angular momentum in multi-electron atoms. This system helps in understanding the energy levels and spectral lines of atoms based on their electronic configurations.