JUDY HOYT: So before we start with today's formal lecture, there's a couple of things I want to talk about. One is the schedule, which I have shown up here. And you'll notice, or if you remember, I've actually shifted around one of the lectures. Here we are today, I think October 19. And we're supposed to have this lecture on the SUPREM-IV process simulator. I decided I wanted to do that lecture later, primarily because I want to have talked about transient enhanced diffusion and those effects. A lot of the examples I show and how to use SUPREM relate to transient enhanced diffusion. And I realized I hadn't really-- I wouldn't have introduced it. So we're going to have instead the ion implantation lectures. There's four on ion implantation, two of those are on TED, and then we'll do that lecture. And as I mentioned also because of the Red Sox game last night, I don't have homework number 4 ready to go out to you yet. And so we c...
PROFESSOR: The molecules and Born-Oppenheimer approximation. OK, we all know that molecules are a lot harder to solve than atoms, and even atoms are not that easy once you have more than one electron because of the electrostatic repulsion, but molecules are significantly different in that one of the greatest simplicities that we had with atoms is that the atom is such that the potential created by the nucleus is spherically symmetric. When you have a molecule you have separate nuclei and therefore your spherical symmetry is gone, and whether you have one electron or more than one electron, there is no spherical symmetry. All our tools of angular momentum don't help us much. We have to start the problem anew. So the difficulty with molecules is basically that the potential for the electrons, where they move is not spherically symmetric. There is another thing that helps us, however, is that there's a nice separation of mass scales. You have the mass, little m, of t...
[SQUEAKING] [RUSTLING] [CLICKING] HONG LIU: So in the last lecture, we have concluded the discussion of fermions. And now, we go to the last missing piece before we can talk about the QED. It's how to quantize the Maxwell field, OK? How to get photon, OK? And so today, we start. OK? So this is a short chapter. I think we should be able to finish it just this week in two lectures. So first, let me just remind you of some aspects of the classical Maxwell theory. And then we will talk about this quantization, OK? So the Lagrangian, say, for the classical Maxwell theory can be written as-- Lagrangian density can be written as F mu nu. So F mu nu is just the standard-- partial mu A nu equal to partial nu A mu. And the J mu is just the electromagnetic current. OK. J mu just electromagnetic current. OK. And then so from this Lagrangian density, then you can derive the equation motion, which is just the Maxwell equation, OK? So the Maxwell equation is given by partial mu F mu...
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