[Jz]

Hi, I'm a new postgrad student from a physics and math background, however for my postgrad project, I need to gain some knowledges on molecular transition. In particular, because I'm interested in molecular spin qubit for quantum information technology, I want to understand all the spin relaxation and dephasing processes that can occur for a molecule. There are many papers out there model the molecule as "two displaced harmonic oscillators" with vibrational and rotational sub-levels lie within the elctronic states. This model usually describes transition between singlet S0 and S1 states and the discussion focuses on internal conversion, nonradiative transition, e.t.c.

Here goes my question: Are internal conversion, intramolecular vibrational relaxation, coupling to environmental phonons and other non-radiative and radiative transitions the relevant processes for spin relaxation? I can't make the connection because these are transitions that occur between singlet S0 and S1 states, where the electron spin does not change (The electron spin only changes from singlet to triplet states). And if they are not, what kind of processes would be dominant for molecular spin relaxation? Thanks for any help in advance.

[Corribus]

Internal conversion generally refers to nonradiative relaxation between electronic surfaces with the same spin multiplicity. Nonradiative relaxation between electronic surfaces with differing spin multiplicity (e.g., singlet to triplet or triplet to singlet) is typically referred to as intersystem crossing. The efficiency of this relaxation (compared to internal conversion) depends on molecular structure, vibronic overlap, the presence of heavy atoms, and etc. Note that there are also radiative analogs that compete with these processes (such as phosphorescence).