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Thread: Electron filmed in motion for the first time

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    Default Electron filmed in motion for the first time

    [ame=http://www.youtube.com/watch?v=IA84LbAuEsA]YouTube - Electron Stroboscope[/ame]



    Researchers have recorded snapshots of electron motion at close to the particle's own natural timescale, which is less than a femtosecond (10-15 seconds). The experiment combines ultrashort light pulses with steady laser light to extract an electron from an atom in a controlled way. With control over the precise moment of extraction, the team was able to cleanly image the electron's quantum state, as they describe in the 22 February Physical Review Letters. This technique could help researchers probe electron-atom interactions in more detail and begin using electrons to observe atoms in the poorly-understood state following ionization.

    One technique for controlling electron motion uses the strong, oscillating electric field of an infrared laser to ionize a cloud of atoms. During each cycle, the field points up, then down, then up again, so it can pull an electron downward and then slam it back up against its atom. The electron scatters off its atom and is then yanked to the right by a steady, sideways electric field, toward a detector. The detected positions of many electrons create an image of the electrons' motion during scattering and also provide information on the state of the recently-ionized atom.

    But this technique lacks precision. From an electron's point-of-view, the laser field oscillates slowly, and it pulls electrons from atoms during a range of times near the moment of peak field strength, rather than releasing them all-at-once. So the resulting image on the detector is fuzzy and represents electrons in a variety of scattering conditions.

    Now a team led by Anne L’Huillier and Johan Mauritsson of Lund University in Sweden has combined this laser technique with precisely timed trains of ultrashort light pulses to cleanly image electron motion. The pulses in the train were just three hundred attoseconds (10-18 seconds) long. The researchers synchronized the pulse train with the oscillations of a relatively weak infrared laser, so that their cloud of helium atoms received a strong, ionizing "kick" at a precise time during each laser cycle. Each attosecond pulse released a few electrons, some of which were thrown back against their atoms before being pushed sideways and detected.

    Accumulating data from many ionization events, the team created clean images of the quantum state of electrons ionized at a single moment in the laser oscillation cycle. The images are the first of their kind that show such controlled electron-atom scattering. The team calls their system a stroboscope, after another device that uses periodic flashes of light to capture a still image of a hummingbird's wings, for example.

    Each experiment generated a "bullseye" pattern showing the locations in which electrons struck the detector plate. To demonstrate that each image represented precisely one moment during the laser cycle--rather than a range of ionization times--the team shifted the timing of the attosecond pulses with respect to the laser field cycle. If electrons were ionized at a time when the laser field gave them an extra boost upward, the pattern shifted upward; if the ionizing pulse came a half-cycle later, the bullseye shifted downward. This pattern shifting wouldn't have been possible with longer-lasting ionization periods.

    The next step will be further controlling and studying electron-atom interaction in more detail, says team member Kenneth Schafer of Louisiana State University in Baton Rouge. He also hopes researchers will use electrons scattered off their atoms to observe the unsettled state of atoms immediately after ionization.

    Louis DiMauro of Ohio State University in Columbus is impressed by the demonstration of precisely timed ionization and imaging. There’s really no other experiment where you can visualize rescattering," he says. "These are the sorts of experiments that demonstrate that if you have these attosecond pulses you have unprecedented control over electron dynamics that we didn’t have before."
    Last edited by Fernbay; 24-05-09 at 03:33 PM.



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    Now a team led by Anne L’Huillier and Johan Mauritsson of Lund University in Sweden has combined this laser technique with precisely timed trains of ultrashort light pulses to cleanly image electron motion. The pulses in the train were just three hundred attoseconds (10-18 seconds) long. The researchers synchronized the pulse train with the oscillations of a relatively weak infrared laser, so that their cloud of helium atoms received a strong, ionizing "kick" at a precise time during each laser cycle. Each attosecond pulse released a few electrons, some of which were thrown back against their atoms before being pushed sideways and detected.
    Accumulating data from many ionization events, the team created clean images of the quantum state of electrons ionized at a single moment in the laser oscillation cycle. The images are the first of their kind that show such controlled electron-atom scattering. The team calls their system a stroboscope, after another device that uses periodic flashes of light to capture a still image of a hummingbird's wings, for example.
    Didn't get much from the video - could be anything.

    This is an interesting technique - In my early days electrons were thought to inhabit exclusive shells around the central proton. Two in the first ,eight in the second and so on . Havn;t bothered to look at current thinking .

    Pushing the electrons closer to the proton center then would put the electron into a closer orbit still going the same speed around the proton so it would have to fly off wouldn't it ?

    Whats the current thinking on this trash ,do you know?

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    Pauli Principle describes electron orbits, and their energies.

    Your education of electron orbits or "shells" is correct. Still only 2 on the inner orbit and 8 in the next and so on. Electron physics is complex stuff.
    Electrons tend to pair up, they do this is superconductors and they also do it while in their various shells.

    Electrons can only absorb or emit specific energies depending on a number of factors. Their orbit, their host atom and external events like passing photons, electric charge, chemical compounds.... oh my head hurts !
    Ever time I see the Pauli Principle mentioned, I just tend to skip over it.
    I don't need to know how an internal combustion engine works, I just know it powers my car

    Unlike satellites, electrons can not have a variety of orbits. They can ONLY have specific orbits. They cannot exist in the forbidden regions between shells.

    Anyhow, we're all familiar with Lasers, well that's a very good example of this kind of thing in practice. If you have a spectrometer (I do) or a prism to split light and a HeNe laser or Fluro light you can examine this for yourself.
    HeNe lasers are typically Red lasers. But you can also get them in Green and Yellow ! What's the difference between these lasers ? Nothing, the gas inside is the same, just the filters on the mirrors are different.
    When the HeNe gas is excited to a plasma, electrons are stripped from their host atoms. Sometimes it's just a single electon from the outter shell, when a new electron falls into this orbit, it emits a red photon. Sometimes it's an electron from an inner shell, an electron falls in emiting a green photon.
    In some cases, the electron from the outter shell falls into the inner shell emiting a yellow photon and then another electron falls into the outter shell emiting a red photon.
    It's not exactly like that, I've just simplified it so that anybody can understand.

    It can even be taken a step further. If say we have a heavy element like tungsten and we use a very high energy to remove an electron from the inner shell, it can be like pulling a marble out of the bottom of a boob tube !
    Marbles in all the higher compartments come tumbling down, each one emitting a photon as it loses energy. Low energy electrons will just emit microwaves, higher energy Infra Red, or Light. Some will emit UV, but the big time is X-rays. Electrons fall directly into these low orbits emitting very high energy X-ray photons. The higher the energy, the harder the X-rays.

    Given the number of electrons in different orbits for different mass atoms.
    Well it doesn't take long to realise that an electron moving from one place to another provides a whole spectrum of different emitted quanta, which can be used to identify the source atoms, compounds and energies.

    Another example which is available is a fluro light. It makes for an excellent science project for high school students. What is in a fluro tube and how can your prove it ?
    Placing even a small fluro light in a box and allow light to escape through a slit and into a prism when the light can then be scattered onto the wall of a dark room. I use a spectrometer, but if you don't have either (you can buy prisms from Australian Geographic shops) then you can just use an ordinary CD or DVD as a diffraction grating to see the spectral lines. But it takes a little bit of effort to set them up.

    A whole rainbow of colours doesn't appear, only some very specific bands of colours. Very noticeable are a two very distinct lines of Green and one of (ultra) Violet. This is very indicative of Mercury.
    Next is a couple of lines one in particular of Aqua or Light blue which is indicative of Argon. Finally there are a whole range of red and orange lines which don't correspond instantly or easily identifiable elements or componds.
    These are from the family of phosphors which coat the inside of the tube and help ballance out the colour to give a white appearence.


    The electron video above isn't something particularly new. We've seen freznel patterns in all kinds of applications before. Really, it's not a video of a single electron, but rather a video of trillions of them all behaving in the same way.
    When you use a DVD or CD as a spectrograph, to see these bands of light spectrum.... well, you're doing the same kind of thing.

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    Oh I knew I could count on somebody out there having done this and blogged it.

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    Unlike satellites, electrons can not have a variety of orbits. They can ONLY have specific orbits. They cannot exist in the forbidden regions between shells.
    I know you believe this we've done it before but I don't like the model.I don't see it as probable

    I don't need to know how an internal combustion engine works, I just know it powers my car
    I do, so I can fix it , down to the last bolt or screw

    But OK so they fire a laser at the object and this dislodges electrons from the target object. So whats all this about Lasers?
    Where does the above fit in?

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    I'm sorry that I can't give you more specific functions of how and why electrons fall into these specific slots and cannot exist outside or in between those slots. I really do not want to venture into that level of particle and quantum physics else I won't be able to sleep at night running combinations through my head.

    Electrons are not like planets. Electrons are quantum particals and behave very differently to objects in the macroscopic world.

    If you own a tuning fork, you'll know it resonates at only one frequency and no matter how your strike it, it will always ring at only that frequency.

    Changing the material it's made from changes the frequency. (like changing the atom)
    changing the length of the tuning fork changes the frequency. (like removing an electron from a different orbit)
    Even taping two tuning forks together does not change the frequency of their tuning fork, but instead keeps the existing resonance and creates some new frequencies. (like two atoms forming a compound).

    Anyhow... I just had a skip through some of my nuclear physics books to see if there was some simple Pauli examples. There weren't, I now have a headache. Then I figured wiki might have a simple explination.

    now my headache is worse !

    Once again, I read the science and I'm happy just to know somebody else has done all the hard work to work it out. I've done some of the experiments mentioned myself just because I could and they were fun to do. But that's it.

    If you're going to be an astronaut, sometimes it's benificial not to know how they built the rocket.

    Anyhow tytower. If you don't like a hundred years of peer review on this subject. The best thing is; that you or anybody else can review the science and modify the theory with sufficent evidence.

    About lasers, it has nothing to do with what your shoot them at. It's all about how the laser works. The person responsible for the concept of the laser is Albert Einstein. He did not live to see the construction of the first laser.

    Inside a laser we have a gas (there are other types of lasers). This gas has a resonant frequency, or several resonant frequencies. The mirrors at the ends of the laser (or output coupler) are also filters. They will filter only one of the frequencies which is why lasers are monochromatic. A red trafic light is made up of hundreds of colours of Red. A HeNe laser is only one colour of red and no other.
    An Atom in the tube is excited, by an electron. As the atoms falls back to it's ground state, it emits a photon. the photon travels down the tube and encounters another atom where it is absorbed by that atom, raising it to a higher energy state (the atom is resonant with that frequency). It then drops to a ground state and re-emits the photon.
    All up and down the tube all of the atoms are now ringing at the same frequency, and they are also all in phase. Only certain specific frequencies can exist. In A HeNe as mentioned, it's Red, Green or Yellow. There in no way in hell or earth that you can get a HeNe laser to produce any other colours.

    On the same subject, this is how we know that the Sun is mostly Hydrogen, some Helium and a few other heavier elements. We can see their spectral lines. We can even see how much and what types of isotopes a far away star contains. The spectral lines are so precise that we use them as a reference. When we look at the spectral lines of a galaxy we can tell if an eleptical galaxy is actually a spiral galaxy that we are seeing side on. We can see the dopler shift of the spectral lines on one side of the galaxy shifted towards us and the lines on the other side, shifted away. the amount of shift can be precisely measured and we can determine how fast the galaxy is rotating, and how fast the whole galaxy is moving towards or away from us.


    Each element, compound and configuration in lasers produces unique frequencies and it's all thanks to our friend Pauli. It subject extends into other fields, but I just know it best for electron orbits and spectral bands of atoms.

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    About lasers, it has nothing to do with what your shoot them at. It's all about how the laser works. The person responsible for the concept of the laser is Albert Einstein. He did not live to see the construction of the first laser.
    No I'm not querying this

    In the subjects first posts the laser is fired at a cloud of atoms from which these electrons are ejected and thence detected. Where are you suggesting the electrons are coming from?...the laser?

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    No... given that you know the mass of a bowling ball, and the mass of the pins. Without being able to see the pattern that the pins were arranged in, one can determine the positions by repeatedly bowling the ball and looking at how the pins are ejected.

    It might seem trival on a macro scale as the pins appear to fall randomly and the process is slow. But with electrons and photons the same experiment is conducted trillions of times per second.

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