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The evolution of the X NMR signal intensity during the cross polarisation is a build-up and decay process whose time axis is usually referred to as the "contact time". At short CP contact times, a build-up of X magnetisation occurs, during which the transfer of 1 H magnetisation from nearby spins (and remote spins through proton spin diffusion ...
Crossover experiments allow for experimental study of a reaction mechanism. Mechanistic studies are of interest to theoretical and experimental chemists for a variety of reasons including prediction of stereochemical outcomes, optimization of reaction conditions for rate and selectivity, and design of improved catalysts for better turnover number, robustness, etc. [6] [7] Since a mechanism ...
This series of experiments, each with a different value of t 1, allows for the detection of chemical shifts from nuclei that may not be observed directly in a one-dimensional spectrum. As t 1 is incremented, cross-peaks are produced in the resulting 2D spectrum, representing interactions like coupling or spatial proximity between nuclei. This ...
Polarization can be used to filter out unwanted signals, such as jamming. If a jammer and receiver do not have the same polarization, the jamming signal will incur a loss that reduces its effectiveness. The four basic polarizations are linear horizontal, linear vertical, right-hand circular, and left-hand circular.
The Lennard-Jones Potential is a mathematically simple model for the interaction between a pair of atoms or molecules. [3] [4] One of the most common forms is = [() ()] where ε is the depth of the potential well, σ is the finite distance at which the inter-particle potential is zero, r is the distance between the particles.
In inorganic chemistry, Fajans' rules, formulated by Kazimierz Fajans in 1923, [1] [2] [3] are used to predict whether a chemical bond will be covalent or ionic, and depend on the charge on the cation and the relative sizes of the cation and anion. They can be summarized in the following table:
The Raman cross section for the vibration of the aromatic ring in toluene around 1000 cm −1 is on the order of 10 −29 cm 2 /molecule·steradian. Therefore, the Raman signal is around 26×10 −23 W/molecule·steradian or 3.3×10 −21 W/molecule (over 4π steradians). That is 0.014 photon/sec·molecule.
Ab initio quantum chemistry methods are a class of computational chemistry techniques based on quantum chemistry that aim to solve the electronic Schrödinger equation. [1] Ab initio means "from first principles" or "from the beginning", meaning using only physical constants [ 2 ] and the positions and number of electrons in the system as input.