OSCILLATOR-STRENGTHS FOR THE W3-DELTA-U-X1-SIGMA+G BAND SYSTEM OF MOLECULAR NITROGEN

Bands of this highly forbidden transition have been observed thus far in absorption only. In fact, emission of the Wu3Xg+1 system is not to be expected from vibrational levels above W(0), since these levels are more rapidly depleted by Wu3B g3 transitions. For W(0), however, the 1/2 3 factor so heavily favors the WX that a progression of partially developed emission bands is to be expected in the 2000- region (when collisional deactivation is low.) These emissions are also favored by the circumstance that the Wu3 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- region to yield f numbers for several bands of the WX system of N2. From these, transition probabilities for absorption and emission between the various levels of the Wu3 and the ground state Xg+1 have been calculated. For the Wu3 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 Wu3Xg+1 and Wu3B g3 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 1/4m. The predominance of the ultraviolet is not clearcut, however, with one of the three spin components more directed to the infrared and with a J-dependent branching ratio all across the band. Thus the measured lifetime for the Wu3 v=0 must be given as an intricately averaged value for just two of the spin components. It is found to be 4 sec, a lifetime which can be realized only in low-collision environments. Parameters are favorable for lasing to the B g3 v=0 level. © 1979 The American Physical Society.