mahela007 Posted July 6, 2009 Share Posted July 6, 2009 How can X-Rays ionize air? (or other molecules) Link to comment Share on other sites More sharing options...
insane_alien Posted July 6, 2009 Share Posted July 6, 2009 simple, they hit the other molecule. specifically the electrons of said molecule/atom. the xray photon has sufficient energy to eject the electron from its orbital, much like if i stuck a cattleprod into you you'd jump out of your comfy chair. this is ionization. Link to comment Share on other sites More sharing options...
mahela007 Posted July 6, 2009 Author Share Posted July 6, 2009 That would be a positive ion right? The whole problem occurred to me when I was reading about Millikans famous oil drop experiment. I read that he used X-Rays to charge some of the oil drops.. (they way I understood it the oil drops got a negative charge.. ) So how could the X-rays give the oil droplets a negative charge? Link to comment Share on other sites More sharing options...
insane_alien Posted July 6, 2009 Share Posted July 6, 2009 i'm not sure, i've done that experiment and x-rays were not used at all. the charge came from friction with the atomizer like how you can charge a plastic rod using a cloth. i have never actually heard of it being done with x-rays. Link to comment Share on other sites More sharing options...
swansont Posted July 6, 2009 Share Posted July 6, 2009 That would be a positive ion right?The whole problem occurred to me when I was reading about Millikans famous oil drop experiment. I read that he used X-Rays to charge some of the oil drops.. (they way I understood it the oil drops got a negative charge.. ) So how could the X-rays give the oil droplets a negative charge? If you ionized the air, you have liberated electrons. They become attached to the oil drops. And apparently he did do it this way http://www.juliantrubin.com/bigten/millikanoildrop.html http://chem.ch.huji.ac.il/history/millikan.html Link to comment Share on other sites More sharing options...
mahela007 Posted July 6, 2009 Author Share Posted July 6, 2009 sorry to be so persistent .... but how do electrons "stick" to oil? Link to comment Share on other sites More sharing options...
swansont Posted July 6, 2009 Share Posted July 6, 2009 sorry to be so persistent .... but how do electrons "stick" to oil? Like they'd stick to any other molecule — electromagnetically. Molecules can attract extra electrons; some do this better than others. Link to comment Share on other sites More sharing options...
mahela007 Posted July 6, 2009 Author Share Posted July 6, 2009 whoops... I forgot my chemistry classes. Link to comment Share on other sites More sharing options...
Liquid Nitrogen Posted July 7, 2009 Share Posted July 7, 2009 How can X-Rays ionize air? (or other molecules) The source ionizes the air and remove electric charges on the material. Link to comment Share on other sites More sharing options...
insane_alien Posted July 7, 2009 Share Posted July 7, 2009 bit late t the party aren't you? also, when answering try to answer the question rather than just defining part of the question which presumably the poster already knew. Link to comment Share on other sites More sharing options...
McCrunchy Posted July 13, 2009 Share Posted July 13, 2009 Just to give you some numbers, a photon in the X-ray domain has an energy typically around 8000 eV, whereas an electron's binding energy can be at most -13.6 eV, level 1s 's energy in hydrogen. So you have plenty of energy to pick it from the atom. This effect is put to practical use in X-ray gas detectors : they're filled with a neutral gas, typically xenon (which won't oxidize you're device once ionized), at a given pressure. When an X-ray goes through the gas chamber, it ionizes the gas. The released electrons are accelerated by an electric field to a cathode, where they read out as a small current. McCrunchy Link to comment Share on other sites More sharing options...
insane_alien Posted July 13, 2009 Share Posted July 13, 2009 whereas an electron's binding energy can be at most -13.6 eV, level 1s 's energy in hydrogen. So you have plenty of energy to pick it from the atom. its only -13.6 eV in hydrogen. helium is more like -25eV Link to comment Share on other sites More sharing options...
McCrunchy Posted July 13, 2009 Share Posted July 13, 2009 oops, indeed. Somehow I had imagined the electron-electron repulsion would make the ionization potential smaller than that of hydrogen ... but it's true we can almost neglect this repulsion to compute the energy levels [ and why is that again ? drifting from the initial subject ...] Link to comment Share on other sites More sharing options...
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