19 posts on chemistry. All posts · RSS feed
Abstract Most textbooks and lecture notes on molecular spectroscopy assert that the most intense transition in the pure rotational (microwave) absorption spectrum () of a closed-shell, diatomic molecule is given, as a function of temperature, by the formula (where is the molecule's rotational constant and …
This previous article derived the form of the kinetic energy operator for a diatomic molecule with the space-fixed origin at the molecular centre of mass: where is the reduced mass of the nuclei, is the electron mass, is the total molecular mass (including the electrons), …
The molecular kinetic energy operator for a diatomic molecule may be written where and are the momentum operators for the two nuclei and electrons, respectively. are the masses of the nuclei and is the electron mass. The vector differential operator del is and being the …
The water–gas shift reaction is a gas-phase reaction, widely used in industry, between carbon monoxide and water to form carbon dioxide and hydrogen: This equilibrium can be analysed in terms of the Gibbs free energy of its constituents as a function of composition and temperature: …
The molar constant-pressure heat capacity, of many diatomic molecules above room temperature shows an increase from roughly to around and then higher as temperature increases. For example the graph below plots as a function of for the molecules , , , .
Simple chemical reactions can be balanced by inspection. For example, for the following reaction: since the number of each type of atom must be the same on each side of the reaction, one molecule of ethanol () must produce two molecules of and three of …
This previous post introduced a simple molecular dynamics simulation for the equilibration of the speeds of the particles of an ideal gas. The present post extends the code a little to model the effusion of an ideal gas through a small hole into a vacuum.
The Morse oscillator code introduced in a previous blog post can be used to visualize the vibronic transitions in a diatomic molecule by creating two Morse objects (one for each electronic state) and plotting their potential energy curves and energy levels on the same Matplotlib …
Note: This post has been updated to use the new scipy.special.sph_harm_y function, which has a slightly different call signature to the deprecated scipy.special.sph_harm function (to be removed in SciPy version 1.17.0.) The spherical harmonics are a set of special functions defined on the surface of …
The Morse oscillator is a model for a vibrating diatomic molecule that improves on the simple harmonic oscillator model in that the vibrational levels converge with increasing energy and that at some finite energy the molecule dissociates. The potential energy varies with displacement of the …
