In the Born-Oppenheimer approximation, we froze the position of the nuclei to find the electronic energy. The position of the nuclei was considered as a parameter that can be modified and we were able to construct the Lenard-Jones potential for
Chapter 6 : MPC – The LCAO theory
This theory says that each molecular orbital Φa is described by a linear combination of atomic orbitals {χ} centred on the M nuclei of the molecule. The molecular orbitals have the symmetry of one of the irreducible representations of the group
Chapter 5 : MPC – The methods of approximation and the quantic chemistry
We have seen quite a lot of new stuff up to now. We described monoelectronic and polyelectronic atoms and developed the description to molecules through the approximation of Born-Oppenheimer, the theory of groups and the CSOC. All of this teaches
Chapter 4 : MPC – Orbital angular moment L
The electrons revolving on an orbital generate an angular moment. ML is the quantic number associated to the projection of L on the internuclear axis. The projection is degenerated because it can either be in the positive values of the z
Chapter 3 : MPC – Group’s theory
Because of the particular geometries of some molecules, the CSCO may be different. Instead of the CSCO that we had with the atom, we want to determine the CSCOH: the complete set of operators commuting with Ĥ. It is thus
Chapter 2 : MPC – Molecules and Born-Oppenheimer
The Hamiltonian quickly becomes monstrously difficult when several atoms and electrons are considered. To illustrate this point, the equations of the Hamiltonians for H, H2+ and H2 are showed below: For a molecule with M nuclei of atomic number Z1, Z2, Z3,
Chapter 1 : MPC – polyelectronic atoms
The presence of a second electron induces a term of repulsion between electrons. This term is positive so it increases the energy of the orbitals. The rest of the equation is similar to the Hamiltonian of the hydrogen. We can compare
Chapter 10 : molecular physical chemistry – operators
Operators can be applied to the wave functions and respect the equation of Schrödinger. The operator inversion Î is an operator such as, if a central symmetry can be found, For instance, the orbital s have a centre of symmetry.
Chapter 9 : Molecular physical chemistry – the hydrogen
To begin smoothly, we will describe the simplest uncharged molecule: the hydrogen. It is composed of one proton with a positive charge e and one electron of opposite charge –e that revolves around the proton at a distance r. In
Chapter 8 : mass spectra – exercises
The solutions immediately follow the problems. You can use this website to find fragments corresponding to a given m/z ratio: MS fragments. The methodology to obtain the answer is given. Problem 1 The two following spectra come from two isomers with