Such a process is called the Auger process, and it occurs in an extremely short time, so it has been difficult to observe the details.However, this time, joint research teams such as Tohoku University, Turku University in Finland, Heidelberg University in Germany, Paris Sacre University in France, Kyoto University, Hiroshima University, RIKEN, and High Brightness Photon Science Research Center have joined the Japanese X-ray. At the free electron laser facility SACLA, we succeeded in capturing an ultrafast reaction that is completed in several tens of femto seconds (10 femto second is one thousandth of a second) after irradiating polyatomic molecules with X-rays.

　In this study, we observed the process of irradiating Jodomethane molecules, in which two hydrogen atoms in methane molecules were replaced with iodine atoms, with X-rays. Molecules irradiated with X-rays become unstable with high energy, and relax to a stable state with lower energy while emitting electrons.At the end, it will fall apart and the ionized atoms will pop out, but if another laser beam is applied during relaxation, the ions that pop out at the end will change.The research group detected the popping out ions and investigated what kind of change occurs depending on the irradiation timing of the laser beam.Then, it was found that the time during which the state in the middle of the relaxation process exists is about several tens of femtoseconds.We also found that not only the Auger process but also a process called interatomic Coulomb relaxation is involved in this ultrafast reaction.

　Irradiation of biomolecules with X-rays causes the destruction of molecules called radiation damage, but the mechanism has not yet been elucidated.If this result leads to the elucidation of the radiation damage mechanism, it is expected that radiation therapy can be carried out accurately and efficiently.

Paper information:[Nature Communications] Real-time observation of X-ray-induced intramolecular and interatomic electronic decay in CH2I2