Please turn on javascript in your browser to play chess.
Science Forum

Science Forum

  1. 29 Jul '13 20:45 / 6 edits
    http://physicsworld.com/cws/article/news/2013/jul/29/how-to-make-zeptosecond-x-ray-pulses

    “....A technique for producing radiation pulses that endure for less than one attosecond (10–18 s) has been proposed by researchers in Spain and the US. If the technique can be realized in the lab, then it could produce X-ray flashes brief enough to capture the movement of an atom's inner electrons or perhaps even look directly at the movement of protons and neutrons during nuclear fission or fusion.
    ...
    ...”


    the video for that is:

    http://physicsworld.com/cws/article/multimedia/2013/may/23/can-we-see-the-motion-of-electrons-on-the-atomic-scale

    Interesting stuff.
    I wonder if this could also lead to a way to help study organic chemical reactions involving enzymes in living cells?
    Or would the necessary presence of water for that make that impractical with no possible practical workaround?
  2. Standard member DeepThought
    Losing the Thread
    30 Jul '13 00:25
    Originally posted by humy
    I wonder if this could also lead to a way to help study organic chemical reactions involving enzymes in living cells?
    [/b]
    Funnily enough they were doing this twenty years ago when a fellow D.Phil. (=PhD) student who did plasma physics was working in this area. In those days they were proud of getting a snap-shot of a cell without it dieing until after they'd taken the picture. The traditional way of doing microscopy on cells before then was to coat the poor thing in gold first - so old info is of a dead or dieing cell. With modern techniques the cell doesn't die until after the picture has been taken. They've probably got the resolution down a little in the mean time, but what you are describing has existed for a while.
  3. Standard member sonhouse
    Fast and Curious
    30 Jul '13 16:34
    Originally posted by DeepThought
    Funnily enough they were doing this twenty years ago when a fellow D.Phil. (=PhD) student who did plasma physics was working in this area. In those days they were proud of getting a snap-shot of a cell without it dieing until after they'd taken the picture. The traditional way of doing microscopy on cells before then was to coat the poor thing in gold ...[text shortened]... solution down a little in the mean time, but what you are describing has existed for a while.
    Any idea of how many cycles of those wavelengths are generated in say one attosecond? or one Zepposecond? A wave of RF 186,200 miles wide would propagate across in one second, for instance. If there is such a thing
  4. Standard member DeepThought
    Losing the Thread
    30 Jul '13 17:55
    Originally posted by sonhouse
    Any idea of how many cycles of those wavelengths are generated in say one attosecond? or one Zepposecond? A wave of RF 186,200 miles wide would propagate across in one second, for instance. If there is such a thing
    An attosecond is 10^-18s, light travels about 1 foot in a nanosecond so this is .3*10-9 metres - or 0.3 nm. X-rays have a wavelength of 0.01 to 10 nanometres, so up to about 30 depending on how hard the X-rays are.
  5. Standard member sonhouse
    Fast and Curious
    31 Jul '13 13:11 / 1 edit
    Originally posted by DeepThought
    An attosecond is 10^-18s, light travels about 1 foot in a nanosecond so this is .3*10-9 metres - or 0.3 nm. X-rays have a wavelength of 0.01 to 10 nanometres, so up to about 30 depending on how hard the X-rays are.
    So a visible photon at say 600 Nm, green, would never be able to supply a 1 attosecond pulse. Looks like 1 wavelength of 600 nm light would be about 3 femtoseconds so that would be the minimum time scale you could hit something with green light. Does that sound about right?
  6. Standard member DeepThought
    Losing the Thread
    01 Aug '13 13:29
    Originally posted by sonhouse
    So a visible photon at say 600 Nm, green, would never be able to supply a 1 attosecond pulse. Looks like 1 wavelength of 600 nm light would be about 3 femtoseconds so that would be the minimum time scale you could hit something with green light. Does that sound about right?
    c = 0.3*10^9 m/s = 0.3 m/ns = 0.3 nanometres per attosecond.
    wavelength = speed /wavelength = speed *period
    period = wavelength/speed = 600 / 0.3 = 2000 as = 2 femtoseconds.
    So yes, but this is a fairly low, lower bound, you need to multiply that by a "life's not perfect" factor to give around say 50 to 100 femtoseconds.
  7. Standard member sonhouse
    Fast and Curious
    01 Aug '13 14:00
    Originally posted by DeepThought
    c = 0.3*10^9 m/s = 0.3 m/ns = 0.3 nanometres per attosecond.
    wavelength = speed /wavelength = speed *period
    period = wavelength/speed = 600 / 0.3 = 2000 as = 2 femtoseconds.
    So yes, but this is a fairly low, lower bound, you need to multiply that by a "life's not perfect" factor to give around say 50 to 100 femtoseconds.
    What about the single photon emitters? Don't they have to have low femtosecond time scales? It would seem they would have to by definition, if one wavelength of green light is 2 or 3 femtoseconds long then it seems that kind of emitter would have to have that kind of time scale.