Problem 8.2.2^∗

Statement

8.2.2^∗. A container filled with air at room temperature and atmospheric pressure is irradiated with X-rays, which ionize a small fraction of the molecules. The negative ions are O$_2$ molecules that have "captured" an electron. The dimensions of the container are $10 \times 10 \times 2$ cm; two $10 \times 10$ cm walls are made of metal, and the others are made of insulating material. A voltage of $1000$ V is applied between the conducting walls, producing a current of $1.5$ μA. Assuming that the numbers of positive and negative singly charged ions are equal, estimate the fraction of ionized gas molecules. The mean free path of the ions is $10^{-7}$ m.