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Spark Plasma Diagnostics
Published in Andreas Schmidt-Ott, Spark Ablation, 2019
Attila Kohut, Gábor Galbács, Zsolt Geretovszky
A widely used optical method for deriving the electron concentration in a plasma is based on the Stark effect, which relies on the splitting of energy levels in an external electrical field, which dominantly depends on electron impacts, while the electric microfields of ions have a minor contribution [31]. Since the splitting of energy levels results in a strong overlap, in most practical cases the Stark effect manifests itself as the broadening of spectral lines (hence also known as “Stark broadening”). The method for calculating the electron concentration based on Stark broadening is predominantly used for the atomic lines of hydrogen or argon [21–24], for which the Stark broadening of spectral lines is a largely linear function of Ne. For example, in argon gas, according to Konjevic [31] () W(Ne,Te)=we(Te)⋅Ne⋅10−17cm3
Absorption/Emission Spectroscopy and Spectral Lines 5
Published in Caio Lima Firme, Quantum Mechanics, 2022
The Stark effect is similar to Zeeman effect where the applied field changes from magnetic to electric. Then, the Stark effect is the splitting of the spectral lines of light (from emission spectroscopy of a determined substance) under the influence of an electric field. No classical explanation could account for this effect. Bohr and coworkers were the first to rationalize theoretically to this phenomenon using the principle of correspondence (see Chapter seven). Afterwards, Schrödinger used a new theoretical approach to calculate the splitting of the spectral lines from the Stark effect (Schrödinger 1926).
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Published in Chunlei Guo, Subhash Chandra Singh, Handbook of Laser Technology and Applications, 2021
Besides natural broadening other mechanisms of homogeneous broadening exist, for example: In a crystal, the constituent particles of the lattice are in constant vibrational motion. This collective vibration can be treated as being equivalent to sound waves bouncing around inside the crystal. These sound waves, just like electromagnetic waves, can only carry energy in quantized amounts. These packets of acoustic energy are called phonons and are analogous in many ways to photons. The principal differences between them are that phonons travel at the speed of sound and can only exist in a material medium. Collisions of phonons with the particles of the lattice perturb the phase of any excited, emitting particles present. This type of collision, which does not abruptly terminate the lifetime of the particle in its emitting state, is called a soft collision.By pressure broadening, particularly in the gaseous and liquid phases, interaction of an emitting particle with its neighbours causes perturbation of its emitting frequency and subsequent broadening of the transition. This interaction may arise in a number of ways: Collisions with neutral particles, which may be soft or hard. A hard collision causes abrupt decay of the emitting species.Collisions with charged particles. These collisions need not be very direct but may involve a very small interaction that occurs when the charged particle passes relatively near, but perhaps as far as several tens of atomic diameters away from, the excited particle. In any case, the relative motion of the charged and excited particles leads to a time-varying electric field at the excited particle that perturbs its energy states. This general effect in which an external electric field perturbs the energy levels of an atom (molecule or ion) is called the Stark effect; hence, line broadening caused by charged particles (ions or electrons) is called Stark broadening.By van der Waals and resonance interactions (usually small effects). Resonance interactions occur when an excited particle can easily exchange energy with like neighbours; the effect is most important for transitions involving the ground state since, in this case, there are generally many particles near an excited particle for which the possibility of energy exchange exists. Broadening occurs because the possibility of energy exchange exists, not because an actual emission/reabsorption process occurs.
Plasma synthesis of ammonia by asymmetric electrode arrangement
Published in Materials and Manufacturing Processes, 2023
F. Baharlounezhad, M.A. Mohammadi, M.S. Zakerhamidi
The Stark effect describes how spectral lines can be divided or shifted in the presence of external electric fields caused by other particles in the plasma.[71] The Stark effect on hydrogen eliminates the degeneracy of states with the same principal quantum number (n) and the different angular quantum number (l), resulting in the Stark broadening commensurate with the strength of the field. This broadening directly related to electron density in plasma discharge is used to determine plasma density. The Stark broadening of the hydrogen Balmer spectral line was exerted to measure the electron density by analyzing the full-width at half-maximum (FWHM). The FWHM of the Stark broadening relating to the electron density is defined by eq. (2)[72,73]
Anisotropic Stark effect of carbon monoxide: emergent orbital cooperativity
Published in Molecular Physics, 2020
Jibiao Li, Dian Wang, Xiaosong Zhu, Emeka Oguzie
The Stark effect describes spectral shifting and splitting of atoms and molecules due to the presence of external electric fields. Depending on the nature of the couplings between external electric fields and the atoms/molecules, the phenomenon can be quite broad based, ranging from vibrational Stark effect [1–7], to optical Stark effect [8–12], to electronic Stark Effect [13–15]. Usually molecules in external electric fields yield rich physics at three different time scales, from picosecond down to attosecond scales. As exemplified in CO/surfaces [16–21], the vibrational Stark effect takes effect on picosecond time scales and originates from strong couplings between molecular degrees of freedom and electric fields, generating molecular motions associated with populating rovibrational states. The likelihood of controlling rotational and pendular states lays the physical basis for aligning diatomic molecules with static electric fields. On the other hand, the electronic Stark effect usually works on femtosecond time scales. In this regime, electric fields may drive the molecules to generate electron wave packets that operate in a manner akin to Bloch oscillations in solids. As expected, shifts and splittings in electronic spectra can always be observed when an electric field is switched on.