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Excitation and deexcitation: Day 1, P1
Excitation and deexcitation: Day 1, P1
Two atoms of different species.
The atoms are different colors but they have the same mass, and each has one excited state. The “cue ball” atom has approximately five times the spacing between its energy levels as the “object ball” atom. A slider controls the initial velocity of the cue ball atom, the object ball atom is initially at rest. The range of the slider is such that one can give kinetic energy to the cue ball atom slightly higher than its excitation energy, but the initial position of the slider is below the excitation energy of the object ball atom. The velocity of the cue ball atom is constrained to be horizontal, and the two atoms are separated by a horizontal displacement. The model is enclosed by horizontal and vertical walls that are perfectly elastic.
1. When the total energy in the system (which is the initial kinetic energy of the cue ball atom) is lower than the excitation energy of the object ball atom, the energy remains entirely kinetic. Because of the 1-dimensional geometry of the initial conditions, the atoms transfer all the kinetic energy on each collision; they are alternately moving or at rest, much like the “Newton’s pendulum,” but with only two masses.
2. When the initial kinetic energy of the cue ball atom is set above the excitation of the object ball atom but below the excitation energy of the cue ball atom, the first collision excites the object ball atom which moves very slowly but with the telltale “halo” that indicates that it is in an excited state. After the object ball atom bounces off the wall it returns to hit the cue ball atom. In that collision of the object ball atom de-excites and its excitation energy is transferred into kinetic energy of the cue ball atom, which then moves as rapidly as before. On the next collision the object ball atom is again excited and moves slowly, and the cycle repeats.
3. When the initial kinetic energy of the cue ball atom is set above its excitation energy, the first collision will excite the object ball atom which will move more slowly than the cue ball atom. The second collision will de-excite the object ball atom and excite the cue ball atom, which will then move very slowly; the third collision will transfer the excitation to the object ball atom, which will move as quickly as it did before.
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org.concord.mw2d.activity.AtomContainer
excitedstate1$0.mmlfalse
org.concord.modeler.PageElectronicStructureViewer
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org.concord.modeler.PageElectronicStructureViewer
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org.concord.modeler.PageXYGraph
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Time (fs)
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Time (fs)
Kinetic Energy
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org.concord.modeler.PageSlider
org.concord.mw2d.models.MolecularModel
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Adjust the initial speed (in 1000 m/s)
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{value="4500.0", label="4.5"}{value="2000.0", label="2"}{value="4000.0", label="4"}{value="1500.0", label="1.5"}{value="3500.0", label="3.5"}{value="1000.0", label="1"}{value="3000.0", label="3"}{value="5000.0", label="5"}{value="2500.0", label="2.5"}
Execute MW script
org.concord.modeler.PageButton
<html><font size=5><b>Run</b></html>
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org.concord.mw2d.models.MolecularModel
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true
Execute MW script
org.concord.modeler.ActivityButton
<html><font size=5><b>Reset</b></html>
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Reload page
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<html><font size=5><b>Snapshot</b></html>
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org.concord.mw2d.models.MolecularModel
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Take a snapshot
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org.concord.modeler.text.LineIcon0.93010105<html><body face=Verdana><b>Three things to observe:</b></html>-333301
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org.concord.modeler.text.LineIcon0.95010105<html><body face=Verdana><b>Task: find the threshold for excitation of each of the atoms by experimenting with different initial cue ball atom speeds.</b></html>-333301
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org.concord.modeler.PageTextArea
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<html>
<body face=Verdana>What is the minimum speed in order for the cue ball atom to excite the target ball atom? Write down the number displayed in the yellow box in the model's window.
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org.concord.modeler.ImageQuestion300200Lowered Etched
<html><body face=Verdana>Fill in a snapshot image that shows the situation below the threshold to excite the object ball atom:</html>
org.concord.modeler.ImageQuestion300200Lowered Etched
<html><body face=Verdana>Fill in a snapshot image that shows the situation above the threshold to excite the object ball atom:</html>
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20.0
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org.concord.modeler.ImageQuestion300200Lowered Etched
<html><body face=Verdana>Fill in a snapshot image that shows the situation above the threshold to excite the cue ball atom:</html>
org.concord.modeler.ImageQuestion300200Lowered Etched
<html><body face=Verdana>Fill in a snapshot image that shows the situation above the threshold to excite the cue ball atom:</html>
20.0
20.0
4.0
20.0
20.0
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org.concord.modeler.text.LineIcon0.93010105<html><body face=Verdana><b>Question:</b></html>-333301
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org.concord.modeler.PageTextArea
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<html>
<body face=Verdana>Why does it take more velocity to excite the cue ball atom?
</html>
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org.concord.modeler.text.LineIcon120.025101015<html><center><b><font face=Verdana size=4><a href="index.cml">Index</a></font></center></html>-ff0067
org.concord.modeler.text.LineIcon120.025101015<html><center><b><font face=Verdana size=4><a href="excitedstate2.cml">Next</a></font></center></html>-3367
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