What experimental method allows for time resolution in measuring dynamic properties in EPR?

Pulsed EPR, or Electron Paramagnetic Resonance spectroscopy, is the method that provides time resolution for measuring dynamic properties. This technique utilizes short, intense bursts of microwave radiation to excite the electrons in paramagnetic species, which allows researchers to manipulate and observe spin dynamics on very short timescales.

The strength of pulsed EPR lies in its ability to capture transient phenomena, such as electron relaxation times and spin dynamics, which are crucial for understanding the mechanisms of chemical reactions, molecular interactions, and the behavior of radical species. By using pulse sequences, researchers can achieve time-resolved measurements that are not possible with continuous wave techniques.

In contrast, continuous wave spectroscopy does not offer the same level of time resolution because it relies on a continuous application of microwave radiation, which limits its ability to study rapid dynamic processes. Infrared and near-infrared spectroscopy are not suitable for measuring dynamic properties in systems characterized by unpaired electrons, as they are focused on vibrational transitions rather than electron spin transitions. Therefore, when time resolution is required for studying dynamic changes in paramagnetic species, pulsed EPR is the preferred technique.