On the other hand, diatomic cations held in an ion trap can be sympathetically cooled by co-trapped, laser-cooled atomic ions. Therefore, it is not always necessary that a fast cycling transition be used for cooling the motion of the molecular ion, but is only needed to enable quantum state preparation and measurement. This significantly relaxes the constraints on the lifetime of the excited electronic state of the diatomic cation. In this use case, the optical cycling lifetime need only be significantly faster than the population redistribution rate from the environment, typically black-body radiation. While the e.g. black-body redistribution rate is dependent on molecular structure, state lifetimes < 1 ms would appear to allow for quantum state preparation and measurement in most scenarios.