An excited molecular level E) is connected with three lower levels [n) and the groundstate (0) by radiative transitions with spontaneous probabilities Aio=4107 s, Ai1 = 3 107 s-, A2 = 1107 s-1, A3 = 5107 s-. (a) Calculate the spontaneous lifetime t, and the relative population densi- ties N/N under cw excitation of li) when t1 = 500 ns, T2 = 6 ns, and T3 = 10 ns.