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XAFS has become one of the fundamental research tools to study structure and electronic states from noncrystallinematerials. With the increase of available photon flux at synchrotron facilities, time-resolved XAFSexperiments can be carried out. Quick-XAFS(QXAFS) is a technique to scan crystal monochromator quickly and canbe used at various synchrotron facilities. Since the system is fairly simple, various detection methods can be used forQXAFS. In general minimum time required a XAFS spectrum is between 10 s and minute. Faster QXAFS systemsthose can obtain a XAFS spectrum in 20 ms are developed and used at some facilities. Dispersive XAFS(DXAFS)is a technique to obtain a XAFS spectrum simultaneously by using a polychromator and a linear detector. DXAFSis suited to study time-dependent phenomena and the time resolution of 2 ms can be realized. DXAFS with sub nstime resolution combined fast detector and single-bunch operation is realized at the Photon Factory. These XAFStechniques are suited to study non-reversible reactions. The meaning of apparent time resolution is different forQXAFS and DXAFS and it will be discussed.
On the other hand, so called "pump and probe" technique can realize much shorter time-resolution such as 100 psor less for repeatable changes. Laser pump and X-ray probe techniques is usually used. This technique is usuallyused to study unstable state.
Future prospects of time-resolved XAFS will be shortly discussed.
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