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cloudy-astrophysics / bug-tracker-migration-test

Trial run for importing the nublado.org Trac tickets as GitHub issues
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l-changing due to collisions by heavy particles (trac #108) #110

Open cloudy-bot opened 15 years ago

cloudy-bot commented 15 years ago

reported by: @CloudyLex

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

Migrated from https://www.nublado.org/ticket/108

{
    "status": "new",
    "changetime": "2019-02-04T12:10:21Z",
    "_ts": "1549282221449479",
    "description": "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?\n\nthe equation in osterbrock implicitly assumes electron colliders.  Burgess & Tully (2005) has useful formalism which could be applied for this situation.\nJ. Phys. B: At. Mol. Opt. Phys. 38 (2005) 2629\u20132644 ",
    "reporter": "gary",
    "cc": "",
    "resolution": "",
    "time": "2009-10-30T17:50:30Z",
    "component": "etc",
    "summary": "l-changing due to collisions by heavy particles",
    "priority": "major",
    "keywords": "",
    "version": "trunk",
    "milestone": "c19 branch",
    "owner": "nobody",
    "type": "enhancement"
}
cloudy-bot commented 15 years ago

@CloudyLex changed version from "C08.00" to "trunk"

cloudy-bot commented 15 years ago

@CloudyLex commented:

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.

cloudy-bot commented 15 years ago

writeup of the theory for heavy particle collisions

cloudy-bot commented 15 years ago

@peter-van-hoof-noaccount commented:

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

cloudy-bot commented 15 years ago

@ryan-porter-noaccount changed milestone from "C10 branch" to "C12 branch"

cloudy-bot commented 15 years ago

@peter-van-hoof-noaccount changed milestone from "C13 branch" to "C19_branch"

cloudy-bot commented 15 years ago

Milestone renamed