Presscurehyphen;InducedaPrime;1Sgr;gplus;thinsp;larr;thinsp;X1Sgr;gplus;Absorption in the Vacuum Ultraviolet Spectrum of Molecular Nitrogen

摘要

TheaPrime;1Sgr;gplus;ndash;X1Sgr;gplus;absorption band of N2, which has been reported recently in a preliminary communication, has been investigated at nitrogen pressures from 10 to 80 torr. A study of the absolute absorption coefficient and of its pressure dependence shows definitely that the observed band arises as a pressurehyphen;induced dipole transition at the quoted pressures. The integrated absorption represents an absolute oscillator strength offthinsp;sol;thinsp;pthinsp;equals;thinsp;3.2thinsp;times;thinsp;10minus;8torrminus;1. The large bandwidth (400 cmminus;1) is attributed to the short duration of the dipolehyphen;inducing collisions: 1.3thinsp;times;thinsp;10minus;14sec on the average. Thus the observed intensity can be interpreted in terms of an average oscillator strength offthinsp;equals;thinsp;0.04per molecule per collision. The apparent optical quadrupole absorptionfvalue of less than 10minus;7corresponds to a very small quadrupole matric element compared to the one which determines the electron excitation cross section. A search for theaPrime;ndash;Xquadrupole emission band in the electronhyphen;beamhyphen;excited spectrum at very low pressures has resulted in strong evidence for the presence of the 0ndash;0 band of this transition, and tentative assignments ofO,Q, andSlines yield approximate values ofugr;0thinsp;equals;thinsp;99 005cmminus;1andB0prime;thinsp;equals;thinsp;1.85thinsp;plusmn;thinsp;0.15cmminus;1.