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Ok I have a problem and since google failed I turn in my desperation to the source of all knowledge.
Teamliquid.net
It's about the same project as my last physics blog in which I asked for a definition of centrifugal repulsion. Well I have come a fair bit further along now but I am totally stuck at the moment.
I have a working program now only that it well does the calculations wrong somehow.
A possible bug might be the normalization of the free wavefunction. Acording the definition of the Einstein coefficient the free wavefunction should be energy normalized. My routine for the free wave function normalizes
it to a phase shifted sine function. This gives the function a dimension of one (I think) which is wrong considering I want an "energy normalized" function (I think). So is there some energy dependent factor that I am forgetting here?
 
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Lol there's no way you're gonna get this one answered...
talk to professor now? :D
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The answer is at the BACK of the textbook.
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can u describe in more detail what you are actually doing?
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I don't know anything... but if your math savvy maybe the equations would help you figure it out? They're all pretty much on wikipedia....
I would start here? http://en.wikipedia.org/wiki/Schrödinger_equation
I have no idea though... just a random guess. or maybe if you know the equations already a math person could help? lol.
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PM micronesia imo. He's a physics teacher. I'm sure he will be only too happy to help you out with all of your homework needs!
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Yea I was hoping that he would read it ~~ (I don't like to pm people for some reason  ) (+ it isn't exactly unlikely that there are a couple of grad students in physics around here ( I am not a grad student mind you))
And aqui: It's a project where the goal is to compare cross sections for a semi classical and a quantum mechanical description of the radiative association reactions in interstellar space.
I managed to reproduce the semi classical results in an article alright but I ran into huge problems in the debugging phase of my quantum program.
The quantum mechanical cross section for such a reaction goes as the integral squared of the wave function for the potential curve on which the atoms are entering the reaction times the transition dipole moment times the wavefunction for the potential on which the atoms are bound. And the integral times the energy of the emitted foton in cube. All summated over all vibritional and rotational states with a bunch of weights etc.
Ehm I didn't bother to type that before because it's largly irrelevant ad would only serve to make a wall of text no one would bother to read.
Anyway my problem was that I think that a possible bug is that the free wave function (the wave function for the potential on which the atoms are entering the reaction) should be energy normalized which I don't think it is (because the dimension doesn't work out) But I don't know how to normalize a wave function with respect to energy and my handler has forgotten, he told me to look for it on the internet but all articels I find just refer to it as "an energy normalized wave function" (Rather than an momentum normalized which is standard)
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cant u just tweak the wave function so it fits your stationary eigenvalue equation Hpsi=Epsi with your desired E?(before the reaction i mean) sry btw if this is completely unappropriatly stupid
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United States24797 Posts
On September 01 2008 20:38 H_ wrote:
PM micronesia imo. He's a physics teacher. I'm sure he will be only too happy to help you out with all of your homework needs!
FU.
I'm not happy to help people. I'm happy to help people for a nominal rate of 100 dollars per hour though.
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And that would be why i didn't pm anyone :p :p
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United States3824 Posts
yeah I don't think anyone has a textbook laying around. Someone can probably check your calculations for you if you put some equations up. Show your work.
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On September 02 2008 02:06 micronesia wrote:Show nested quote +On September 01 2008 20:38 H_ wrote:
PM micronesia imo. He's a physics teacher. I'm sure he will be only too happy to help you out with all of your homework needs! FU. I'm not happy to help people. I'm happy to help people for a nominal rate of 100 dollars per hour though.
micro the going rate is 125$/ hour
you getting ripped off ma friend
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United States24797 Posts
On September 02 2008 02:33 Caller wrote:Show nested quote +On September 02 2008 02:06 micronesia wrote:On September 01 2008 20:38 H_ wrote:
PM micronesia imo. He's a physics teacher. I'm sure he will be only too happy to help you out with all of your homework needs! FU. I'm not happy to help people. I'm happy to help people for a nominal rate of 100 dollars per hour though. micro the going rate is 125$/ hour you getting ripped off ma friend
I give a small discount to starcraft players.
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lol I am trying to figure out what this is about but I am failing miserably.
In layman's terms, this has to do with the strength of radioactive waves being exerted by an atom, given the nature of the orbits of it's electrons?
or am I way off?
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you might get more help if you posted some of your work first =/
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United States24797 Posts
On September 02 2008 03:15 travis wrote:
lol I am trying to figure out what this is about but I am failing miserably.
In layman's terms, this has to do with the strength of radioactive waves being exerted by an atom, given the nature of the orbits of it's electrons?
or am I way off?
If I remember correctly from back when I did any Quantum Mechanics, a wave function is literally a curve/equation that graphs probability versus position, where probability describes how likely the wave/particle will be found at that location. For example, in a small square well, the odds of the wave being found inside the well are big, and outside of the well are small (because it is unlikely for the particle to escape the well of its own accord).
The free wave function means there is no well, wall, potential, what have you... and it turns into a different mathematical problem.
Normalization basically means you scale down the amplitude of the wave function so that the odds of the wave being SOMEWHERE is 100%.
For example:
If you have a 2D square well that's 1 meter wide and 1 meter deep, you can construct a wave function. Assume the particle is not able to jump out of the well. The odds of it being near the wall is ~blah and the odds of it being approximately in the center are approximately blagh...
Suppose we constructed our well in such a way that the odds of it being anywhere in the well are identical to the odds of it being somewhere else in the well (since discrimination is bad in our society). The wave function would simply be a horizontal line over the domain x=0m to x=1m. What should the y value of this line be? Well, if you integrate the curve (calculate the area under the graph) it should add up to 100%. So to get an area of 1, you can just use the area formula in this simplified case:
Area = length * width
1 = 1m * width
width = 1
In this case, the 'width' is actually the y value of the wave function which we already determined was a horizontal line.
The problem regarding the OP has to do with normalization of the wave function for a free particle, which can be tricky and requires fourier transforms IIRC.
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If I remember correctly from back when I did any Quantum Mechanics, a wave function is literally a curve/equation that graphs probability versus position, where probability describes how likely the wave/particle will be found at that location.
the wave function hasnt necessarily anything to do with position. it can describe the probaility for any continous spectrum of eigenvalues.
The problem regarding the OP has to do with normalization of the wave function for a free particle, which can be tricky and requires fourier transforms IIRC.
you add infinite wavefunctions within an finite impulsspectrum to get the free particles wavefunction. if you know the weigthing function (fourier transform in exemplarary cases) its not hard to normalize at all.But i dont think that is what klackon is talking about. he said the wave function in a certain potential. also he wanted to normalize the energy whatever he means by that.
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United States24797 Posts
On September 02 2008 04:46 aqui wrote:Show nested quote +
If I remember correctly from back when I did any Quantum Mechanics, a wave function is literally a curve/equation that graphs probability versus position, where probability describes how likely the wave/particle will be found at that location.
the wave function hasnt necessarily anything to do with position. it can describe the probaility for any continous spectrum of eigenvalues.
I'm trying to put it into somewhat layman's terms lol...
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I might be able to help you with this (I'm a physics grad student) but you need to describe the question better. All you talk about in the OP is the problem with your solution, but I don't understand what it is you're trying to solve.
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In order to use molecular replacement to solve the protein structure of an obtained crystal to which data has been collected from a synchrotron, you must use fourier mathematics and patterson functions.
Although molecular replacement is a powerful technique which allows you to do molecular modeling and refinement, it is easy to choose a biased search model which will adversely affect your generated protein structure. Thus, I would suggest that you use MAD (multiple anomalous data scattering) Phasing to generate the electron density map which can then be modeled in order to solve the structure.
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On September 02 2008 03:15 travis wrote:
lol I am trying to figure out what this is about but I am failing miserably.
In layman's terms, this has to do with the strength of radioactive waves being exerted by an atom, given the nature of the orbits of it's electrons?
or am I way off?
If you take two atoms and make a molecule out of them their total energy is lowered but since the energy of the "universe" must remain constant the excess energy has to go somewhere. Normally a third particle would crash into the forming molecule and absorb this energy as kinetic energy, that is heat.
However in interstellar space there aren't a whole lot of particles flying about so the probability for a 3 body reaction is generally negible.
In this case the excess energy is emitted as a "light particle", a photon. The simplest way to think of a wave function would be as a replacement to the classical trajectory.
When you want to modell two colliding particles you need some way to describe their movements so to speak, when you do the problem quantum mechanically you use wave functions to do that.
Hm and I am not looking for a "solution" so to speak, more like the correct theoretical approach to take when you want to take a momentum normalized wave function and turn it into an energy normalized one. (I don't know where to start)
But anyway my handler mailed me 1 hour or so ago and wrote that he had found the solution in an old article he had lying about.
If you take the momentum normalized function and multiply it with a factor SQRT(2M/pi*SQRT(2M*E)) you get an energy normalized function. (I might remember it slightly wrong will check tomorrow obv)
yay I guess -_-
I don't understand half of this crap as good as i ought to :/
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EPT
