1. The problem statement, all variables and given/known data I want to find the ionization cross section in a mass spectrometer for the gas Argon. The value obtained should be in the 2x10-16 cm2 range. 2. Relevant equations Q = ionization cross section I = K(V,B)xNxQxdxIe Where I = (0.17 x 10-11, K(V,B) =1, d = 0.1 cm, and Ie = 5 x 10-5 Amperes, the trouble is finding N. N is the gas density, but I'm not sure what units it's in. 3. The attempt at a solution To find N, you could use the ideal gas law, PV = nRT, The pressure is known as 1.44x10-3 To find N I said that N = P(Avogadro's constant)/ RT where R = 8.314x106, for it to be in cm3, and T is room temperature in kelvins. The value I get from this is 9.5x10-19, which is too small. Is there something I'm missing here, I need to get in the 10-16 range.