Investigation and probing of internal conversion can be done from either an experimental or theoretical vantage, with their own profits and consequences. An experimental vantage can yield highly accurate findings, as well as allowing for significantly larger systems to be investigated. Experimentally, one is only limited by what can be made. The phase state, temperature, external fields, measurement technique, to name a few of many parameters, can all be altered to probe the physics of a given system. Characterisation is typically performed using ultra-short pulsed lasers , with femto-or attosecond resolution permitting direct observation of relaxation pathways. The limitation here is money; requirements for these measurements is often very expensive, and are therefore not available to many researchers.