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    Hi,

    In a school project we are looking at how different gases absorb radiation. When analysing our results, we found that for incident gamma radiation, the smallest molecules absorbed MORE gamma than those that were bigger.

    For example, the order in molecule size for the gases we tested are as follows (large to small):

    Methane
    Carbon Dioxide
    Oxygen
    Nitrogen
    Helium

    Our results strongly fit this trend. All we wanted to know is WHY the size of the molecule effects it in this way. We used a balloon (inflated to the same size each time and at constant room temp) but have no other measurements in terms of the gases used. Can anyone help please?
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    I have no idea BUT when you say from large to small, they're clearly not ranked in terms of mass or methane would come second last before He.

    Could you look more closely at the bonds? Isn't radiation absorbed by the vibration of the bonds? Do different bonds absorb radiation of different frequencies? In which case is that the effect you're seeing - that the bonds in methane are better fitted to the frequency of the radiation you're testing?

    Sorry, no answers, only questions.
 
 
 
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