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Electron Diffraction to Tchaikovsky Waltz of the Flowers
Did this about 10 years ago for my physics degree final year project - numerical solutions to the time-dependent Schrödinger Equation (TDSE) applied to electron diffraction. Primarily we were interested in the effects of different slit geometries, as this had never been studied before (for example there's no way you could analytically solve Kirchoff's diffraction theory to anything other than 1-D slits, that is, slits without thickness and funny shapes) - all is performed in dimensionless units.
The electron is modelled here as a wavepacket, that is, a Gaussian distribution superimposed with a sinusoidal wave term, and it interacts in the TDSE with the potential boundary of a double-slit wall, I also investigated other potentials and confines, including an elliptical potential, which was an idea based on what was then a recent publication by IBM laboratories on their STM atom manipulation on substrates - in particular the Stadium Corral. I wanted to approximate the effect they observed with wave effects on the surface state electron density, with the peaks at the foci of the ellipse. They observed that an impurity at one focus led to the disappearance of the peak at the other focus, due to the wave nature to the electron distribution. I never quite got that far as it would have required a lot more computing power (and it was way beyond the objective of the project), but focusing of the electron packet can be observed.
The most advanced desktop PCs I had at my disposal were PII 300 MHz machines - I commandeered 4 machines in our IT room (which got me in trouble with IT dept for never logging out - I disabled their auto logout/reboot scripts which ran a disk cleaner, deleting all user files after midnight - they even blocked my account for a couple of days!) - these machines spent the next month solving the TDSE for a number of conditions via the predictor-corrector method, approximating the differential equations with finite steps, in good old Fortran. This method, however, results in two opposing initial directions for the wave packet to move in, hence the electron splits in two.
Time-dependence therefore suggests that the resulting data be presented in some sort of movie (though not just a movie - time averaged plots can and was also done besides this, for comparison with classical diffraction), so the final probability distribution data was then rendered frame by frame in Matlab. At that time Matlab was a bit basic, you couldn't automatically grab each frame and convert into a movie like you can now. Consequently each frame had to be manually saved as a bmp, all 7000 or so, then imported into some basic animation package, I forget what is is now. For a bit of fun I added the marvellous Waltz of the Flowers by Tchaikovsky. Nobody can write music like he did!
The "finé" at the end was a play on the French word for finished - "fini" - all the French people I knew / met at university seemed to say "é" at the end of everything!
Length: 335
Rating: 5.00 (2 ratings)
Tags: electron difrraction qauntum numerial computation time depedent Schroedinger Equation Tchaikovsky Waltz of the Flowers
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PhotoTechEDU Day 8: Diffraction and Interference in Imaging
Google Tech Talks
March 14, 2007
ABSTRACT
Photographic Technology Day 8: This session addresses effects of the wave nature of light. This approach will allow us to talk about the phenomena of interference as well as diffraction. The understanding of the notion of diffraction will be used to determine the Rayleigh criteria and finally the resolving power of an optical system. In the second part of the lecture, we will study gratings using the wave approach. An example of an amateur spectroscope for astronomy using a reflective grating will be shown. Credits: Speaker:Rom Clement
Length: 3286
Rating: 5.00 (2 ratings)
Tags: google howto phototechedu day diffraction
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EE290f - Lecture 17: X-Ray Diffraction for Materials Analysis - given by Dr. Simon Clark, ALS/LBNL
EE 290F Synchrotron Radiation for Materials Science Applications (Sp 07)
Lecture 17 - X-Ray Diffraction for Materials Analysis - given by Dr. Simon Clark, ALS/LBNL
Length: 4751
Rating: 5.00 (3 ratings)
Tags: uc ucberkeley university california berkeley lecture science
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EE290f - Lecture 3: Probing Matter: Diffraction, Spectroscophy and Photoemission - Professor Anders Nilsson, Stanford Synchrotron Radiation Lab
EE 290F Synchrotron Radiation for Materials Science Applications (Sp 07)
Lecture 3 - Probing Matter: Diffraction, Spectroscophy and Photoemission - Professor Anders Nilsson, Stanford Synchrotron Radiation Lab
Length: 4861
Rating: 5.00 (1 ratings)
Tags: uc ucberkeley university california berkeley lecture science
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EE290f - Lecture 7: Multilayer Interference Coatings, Scattering, Diffraction, Reflectivity and Applications
EE 290F Synchrotron Radiation for Materials Science Applications (Sp 07)
Lecture 7 - Multilayer Interference Coatings, Scattering, Diffraction, Reflectivity and Applications
Length: 4858
Rating: 0.00 (0 ratings)
Tags: uc ucberkeley university california berkeley lecture science
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Diffraction Gratings for Lasers - Tutorial
Diffraction gratings from http://www.dragonlasers.com
This tutorial explains what laser diffraction gratings are, the different types, their applications and the care that needs to be exercised when using them.
Laser diffraction gratings are from Dragonlasers at http://www.dragonlasers.com
Length: 209
Rating: 4.80 (11 ratings)
Tags: laser diffraction gratings grating matrix green blue red show display optics
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Blue Laser Pointer Aurora Diffraction
The Aurora is from Dragonlasers at http://www.dragonlasers.com
A simple starburst diffraction grating is used to spread the Aurora's beam with breathtaking results. Absolutely spectacular beam.
http://www.dragonlasers.com
Length: 61
Rating: 4.90 (20 ratings)
Tags: Blue laser pointer aurora dragonlasers
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Red Diffraction on a Blu-Ray
Is it possible to see red light diffraction on a blu-ray disk?
Optical disks like the cd rom, the dvd and the blu ray disk with their fine grid show coloured diffraction. Analysing the reflection of sunlight from a cd rom shows that the two inner spectral rings are both the first order spectrum. Each spot on the cd reflects the spectrum into two directions: to the inside, across the axis to the inner circle and to the outside, to the outer circle. The second order is further outside and widely spread so that it is comparably dark.
The colour for each angle can be calculated and drawn in a chart for the disks. The bluray disk with its 320nm grid shows no diffraction when the light comes perpendicular to the disk surface. When the light comes under the observation angle the path difference is doubled.
This can be done with observing the disk with the light shining over the shoulder of the observer. In this way the cd displays high number of diffractions which mostly overlap to white light. From 80° to 90° the dvd shows the 3. order diffraction which is blue.
And finally the blu ray disk really shows all colours up to red light of 640nm.
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Lichtbeugung an optischen Speichern
Kann man rote Lichtbeugung an einer Blu Ray Disk sehen?
Optische Speicher wie die CD Rom, die DVD und die Blu Ray Disk mit ihren feinen Gitterstrukturen zeigen farbige Reflexionen. Eine genauere Betrachtung des reflektierten Sonnenlichts von einer CD zeigt, dass die beiden inneren Ringe beide zum Spektrum erster Ordnung gehören. Jede Stelle der CD reflektiert das Spektrum in zwei Richtungen, nach innen, über die Achse zum inneren Ring, und nach außen zum äußeren Ring. Das Spektrum zweiter Ordnung liegt weiter draußen und ist damit vergleichsweise dunkel.
Die Farbe für jeden Winkel kann berechnet und in einem Diagramm aufgetragen werden. Für den senkrechten Einfall ergibt sich bei der Blu Ray Disk gar keine sichtbare Beugung. Lässt man das Licht nicht senkrecht zur Scheibe sondern unter dem Beobachtungswinkel einfallen, dann wird der Gangunterschied doppelt so groß.
Man kann sich dazu als Betrachter das Licht über die Schulter scheinen lassen während man die Scheibe betrachtet. Dabei ergeben sich für die CD viele Spektren die sich weitgehend zu weißem Licht überlappen. Im Bereich von 80° bis 90° sieht man so auf der DVD die Beugung 3. Ordnung die an dieser Stelle blau ist.
Auf der Blu Ray Disk sieht man dann in diesem Winkelbereich tatsächlich rotes Licht mit einer Wellenlänge von bis zu 640nm.
Length: 140
Rating: 4.20 (4 ratings)
Tags: diffraction optical disk CD DVD blu-ray light colour physics tutorial experiment
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Diffraction Gratings & green laser Demo Tutorial
Diffractin gratings http://www.dragonlasers.com
Demonstration tutorial of a Viper laser pointer and 3 types of starburst diffraction grating.
Viper is courtesy of http://www.dragonlasers.com
starburst Diffractin grating are courtesy of http://search.ebay.com.au/ws/search/SaleSearch?sofocus=bs&satitle=diffraction+grating&sacat=-1%26catref%3DC5&fbd=1&_trksid=m37&from=R6&nojspr=y&pfid=0&fswc=1&few=&saprclo=&saprchi=&fss=1&saslop=1&sasl=goodly88088&fls=4%26floc%3D1&sargn=-1%26saslc%3D0&salic=15&saatc=15&sadis=200&fpos=2774&fsct=&sacur=0&sacqyop=ge&sacqy=&sabfmts=0&saobfmts=exsif&ga10244=10425&ftrt=1&ftrv=1&sabdlo=&sabdhi=&saaff=afdefault&afcj=&afmp=&fsop=1%26fsoo%3D1&fcl=2&frpp=100
Length: 128
Rating: 4.40 (19 ratings)
Tags: laser lasers lazer lazers portable green pointer pointers powerful high power burn balloon starburst diffraction grating
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