Oscillator strengths for theWΔu3−XΣg+1band system of molecular nitrogen

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Abstract
Bands of this highly forbidden transition have been observed thus far in absorption only. In fact, emission of the WΔu3→XΣg+1 system is not to be expected from vibrational levels above W(0), since these levels are more rapidly depleted by WΔu3→BΠg3 transitions. For W(0), however, the ν3 factor so heavily favors the W→X that a progression of partially developed emission bands is to be expected in the 2000-Å region (when collisional deactivation is low.) These emissions are also favored by the circumstance that the WΔu3 is the N2 state most readily excited by low-energy electrons so that the v=0 level may attain a very large population. The present measurements consist of intercomparisons of absorption bands recorded photographically in the 1500-Å region to yield f numbers for several bands of the W←X system of N2. From these, transition probabilities for absorption and emission between the various levels of the WΔu3 and the ground state XΣg+1 have been calculated. For the WΔu3 v=0 level, however, the calculation of transition probabilities for emission and of a lifetime becomes a rather complicated procedure as a result of the competitive relationship between WΔu3→XΣg+1 and WΔu3→BΠg3 for this one level. It turns out that the forbidden vacuum ultraviolet emission becomes more probable than the permitted emission which falls in the infrared beyond 100 μm. The predominance of the ultraviolet is...