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Cross sectionby touqra
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#1
Jan1708, 05:32 PM

P: 282

What does it mean when they say s wave cross section, p wave cross section .. ?



#2
Jan1808, 01:47 AM

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P: 4,739

http://farside.ph.utexas.edu/teachin...es/node70.html The [itex]l[/itex] that you see in eq 957 is then the "[itex]l[/itex]  QM number". And [itex]l[/itex] is denoted by, 0 = s, 1 = p, 2 = d, etc, same as in atomic physics notation. Semiclassicaly, you can see the [itex]l[/itex] as the classical angular momenta of the incoming particle with respect to the centre of the scattering potential. And also the [itex]l[/itex] is quantisized, so only some values of [itex]l[/itex] are allowed. Now since the sum goes to infinity in eq 957, we cut of where we expect no partial waves to contribute. And that is often assigned by [tex] l_{max} \approx R\cdot k [/tex] Where R is the range of the potential and k is the momenta of the incoming particle (wave number). Now the cross section is proportional to the scattering amplitude modulus square, i.e the modulus square of eq. 965 times a constant with alot of pi's hbar's etc. So the scross section, you only have [itex]l[/itex] = 0 in you sum, and pcross section only [itex]l[/itex] = 1. etc. I hope you got the idea =) 


#3
Jan2208, 01:40 PM

P: 3

Hello,
To munch the QM into an analogy: Another way to look at is  how does one particle look to another. If you assume the target particle to be balllike, then in its basic form (ground state), you'll get the classic 3D crosssection  this is how it will appear to the incoming particle and such it will be scattered from the target particle. But if the particle is excited to a higher state, then it will no longer appear as a ball but something else entirely. And vice versa. Smoochie 


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