[编辑:永太净化设备经营部] [时间:2017-06-09]


So in order to answer this question, we are first to definewhat is the time scale of an electron in an atom. And for that, we can use themodel of a hydrogen atom by Bohr, where you see here a positively charged coreand an electron moving around this core. And to have an idea about the timescale of this electron moving around the core, we can calculate it with thisequation and we end up with a period time of about 100 of attosecond. So whatis an attosecond? An attosecond is about, is actually 10-18 second. Andto give you an idea about what an attosecond is compare to a second. Well, it’sexactly the same as comparing a second to the age of universe. So to accessthis information here of the motion of the electron, what we need is flash oflight extremely fast. And those flash of light are attosecond pulse train. In orderto obtain this attosecond pulse train, we use a process that is called highharmonic generation. That is based on the upconversion of a laser frequency intoits high harmonic. This way we obtain a common frequency that is very large spectrally,which means that in the time domain we obtain a train of an attosecond pulse. Now,what type of information we can get thanks to these pulses. Well, we canactually see electron motion in big, eh, system, like molecules. And we can seethe changes of the molecules and how those changes appear, basically howreaction, a chemical reaction, happen. And the other possibility is also tounderstand how damage in cells happen, because any damages in cells start by amotion of an electron…