Answer Happy

Problem 1 Line Broadening II 5 (3+2) points Which cause for line broadening is dominant in the following cases? (a) Starlight moves through a cloud of hydrogen atoms of particle density n = 105/m³ and temper- ature T = 10 K. Is the natural line width Awy, the Doppler width Awp or the collision width Awc the dominant cause for the broadening of the hyperfine transition and the Lyman a-line? The decay time for the hyperfine transition 1¹S1/2 (F= 0 F = 1) at λ = 21 cm is to = 109 s and the collision cross section to 10-9 s and a = 10-15 cm². = 10-22 cm², whereas for the Lyman a-line A = 121.6 nm, (b) A laser beam of wavelength λ = 3.39 µm and a beam diameter of 1 cm is sent through a methane cell, in which CH4-molecules at T = 300 K absorb on the transition ik (tok = 20 ms). Is the natural line width Awy, the Doppler width Awp, or the flight time width AwFT the largest?