Search results
Results from the WOW.Com Content Network
Resonance hyper-Raman spectroscopy: Excitation of the sample occurs by two-photon absorption, rather than by absorption of a single photon. This arrangement allows for excitation of modes that are forbidden in ordinary resonance Raman spectroscopy, with intensity enhancement due to resonance, and also simplifies collection of scattered light.
Contributing structures of the carbonate ion. In chemistry, resonance, also called mesomerism, is a way of describing bonding in certain molecules or polyatomic ions by the combination of several contributing structures (or forms, [1] also variously known as resonance structures or canonical structures) into a resonance hybrid (or hybrid structure) in valence bond theory.
Acoustic resonance spectroscopy (ARS) is a method of spectroscopy in the acoustic region, primarily the sonic and ultrasonic regions. ARS is typically much more rapid than HPLC and NIR . It is non destructive and requires no sample preparation as the sampling waveguide can simply be pushed into a sample powder/liquid or in contact with a solid ...
The most common method for detecting the mechanical resonant spectrum is illustrated in Fig. 2, where a small parallelepiped-shaped sample is lightly held between two piezoelectric transducers. One transducer is used to generate an elastic wave of constant amplitude and varying frequency, whereas the other is used to detect the sample's resonance.
Triple resonance experiments are a set of multi-dimensional nuclear magnetic resonance spectroscopy (NMR) experiments that link three types of atomic nuclei, most typically consisting of 1 H, 15 N and 13 C. These experiments are often used to assign specific resonance signals to specific atoms in an isotopically-enriched protein.
Clar's rule states that for a benzenoid polycyclic aromatic hydrocarbon (i.e. one with only hexagonal rings), the resonance structure with the largest number of disjoint aromatic π-sextets is the most important to characterize its chemical and physical properties. Such a resonance structure is called a Clar structure. In other words, a ...
Thus resonance is achievable not only about the possible energy-levels of a two-level atom, but also about the sub-levels in the energy created by lifting the degeneracy of the level. If the applied magnetic field is tuned properly, the polarization of resonance fluorescence can be used to describe the composition of the excited state.
In addition to measuring the frequency, the dissipation factor (equivalent to the resonance bandwidth) is often measured to help analysis. The dissipation factor is the inverse quality factor of the resonance, Q −1 = w/f r (see below); it quantifies the damping in the system and is related to the sample's viscoelastic properties.