Is Hydrogen Gas Transparent to Gamma Rays? And What About Xenon Gas?

[Northprairieman]

I remember reading before that hydrogen gas is "transparent" to gamma rays. What does this mean? I know it has something to do with the gamma rays not heating the hydrogen. Also, would Xenon gas be transparent to gamma rays?

 

[turbo]

According to this abstract (haven't bothered reading the paper yet), gamma ray bursts can ionize neutral hydrogen at radii of 50-100 parsecs.

http://arxiv.org/abs/0802.0737

 

[QuantumPion]

I remember reading before that hydrogen gas is "transparent" to gamma rays. What does this mean? I know it has something to do with the gamma rays not heating the hydrogen. Also, would Xenon gas be transparent to gamma rays?

The probability of a gamma ray to interact with matter is dependent on the mass of the atom and the density of the substance. Because hydrogen is light, and at atmospheric conditions the density is very low, gammas are attenuated very little compared to water or lead. If hydrogen was liquefied and pressurized, it would attenuate more gammas (but still not as much as water since hydrogen is still lighter then a water molecule).