Opened 8 years ago

Last modified 7 years ago

#108 new enhancement

l-changing due to collisions by heavy particles

Reported by: Gary J. Ferland Owned by: nobody
Priority: major Milestone: C13 branch
Component: etc Version: trunk
Keywords: Cc:


l-changing and n-changing collisions in the iso-sequences with heavy colliders are suspect. for an arbitrary collider what is the relationship between the collision strength and cross section for heavy colliders?

the equation in osterbrock implicitly assumes electron colliders. Burgess & Tully (2005) has useful formalism which could be applied for this situation.

  1. Phys. B: At. Mol. Opt. Phys. 38 (2005) 2629–2644

Attachments (1)

coll_strength4.pdf (47.4 KB) - added by peter 8 years ago.
writeup of the theory for heavy particle collisions

Download all attachments as: .zip

Change History (5)

comment:1 Changed 8 years ago by Gary J. Ferland

Version: C08.00trunk

comment:2 Changed 8 years ago by Gary J. Ferland

2010 Feb 04, Peter sent the following:

Ticket 108 is the heavy particle collision collision strength question. Ryan and I talked about this a few days ago. I thought he said it was fixed to Peter's and his satisfaction. Can we clear this ticket? Gary

That is not entirely my recollection. I remember Ryan saying that we should sort this out, but I don't remember anything happening after that. For me there are still several questions open regarding the heavy colliders:

1) is the assumption on how to convert an electron impact into a heavy particle impact in my write-up correct? This is needed because VS80 only treats electron impact and we need some way to approximate heavy particle impact. We eventually got to the point where we thought that assumption came from Jackson, but we never really got to the source. The assumption I made in the writeup is nothing more than an educated guess about what it might have been.

2) there was a disagreement about the definition of the energy of the incoming particle that VS80 used, at least that is how I remember it. I would have to look up the paper to remember the exact details. At the time I looked, the definition used in the code did not agree with my interpretation of the VS80 definition.

3) there is the issue of the crude approximation that is used to calculate the cross section (evaluate the CS at kT rather than do the integral). This was solved for electron impact, but as far as I know the issue still stands for heavy particle impact. Certainly for transitions with (essentially) zero oscillator strength a very easy exact analytic solution for the integral would be possible.

Changed 8 years ago by peter

Attachment: coll_strength4.pdf added

writeup of the theory for heavy particle collisions

comment:3 Changed 8 years ago by peter

The educated guess referred to above is Eq. (1) in the writeup attached to this ticket.

comment:4 Changed 7 years ago by Ryan Porter

Milestone: C10 branchC12 branch
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