Due to the presence everywhere of the cosmic background radiation, the minimum p
ID: 1305118 • Letter: D
Question
Due to the presence everywhere of the cosmic background radiation, the minimum possible temperature of a gas in interstellar or intergalactic space is not 0 K but 2.7 K. This implies that a significant fraction of the molecules in space that can be in a low-level excited state may, in fact, be so. Subsequent de-excitation would lead to the emission of radiation that could be detected. Consider a (hypothetical) molecule with just one possible excited state. (a) What would the excitation energy (in terms of
Explanation / Answer
a)
Using given equation:
31 = 100 e- [ Ex - Eo] / kT
0.31 = e- [ Ex - Eo] / kT
-1.17 = -[ Ex - Eo] / kT
1.17 x 1.38 x 10-23 x 2.7 = Ex - Eo
4.36 x 10-23 = Ex - Eo
delta E = 4.36 x 10-23 J = 272.74