Spin-spin coupling, or J-coupling, can be observed in the low-field NMR experiments in a liquid phase at a room temperature. It is typically of the order of 100 kHz, or less. The effective Hamiltonian for J-coupling has a form: J (I1 dot I2), where I1 & I2 are nuclear spins and J is a scalar coupling constant, which depends on the molecule. This coupling survives averaging over molecular rotations and leads to a narrow resonant line at the frequency (J/h) Hz. Generally, there is also a vector coupling of the form (J1 dot I1 cross I2). Because of the inversion symmetry J1 must be an axial vector. Such vector is allowed only for chiral molecules, which have helix structure. If parity is not conserved, J1 can be a polar vector and such coupling can be observed for any non-chiral molecules. To avoid averaging by rotation one has to apply external electric field. The idea of the experiment is very similar to the beam experiment in Yale. I will show that it is possible to make a rather accurate analytical estimate of the P-odd vector coupling for any diamagnetic molecule with only one heavy nucleus.
Host: David DeMille