Rotational Structure of Some Electronic Bands of Chlorine Dioxide

摘要

The rotational structure of several violet absorption bands of ClO2has been studied. The bands considered correspond to the vibration transitions (v1prime; 0 0)larr;(0 0 0) wherev1prime; = 1, 2, 3, 4, and 5. The most prominent identifiable feature of the rotational structure is a doubletqQbranch resolved in the tail of each band. Forv1prime; = 1, 2, and 3, the rotational wave numbers of these branches are given byngr;1,2requals;minus;12lpar;0.0615plus;0.0042v1prime;rpar;Llpar;Lplus;1rpar; minus;12lpar;1.188plus;0.008v1prime;rpar;K2plus;0.13Lplus;0.174lpar;v1prime;minus;0.4rpar;K mnplus;12lsqb;0.109lpar;2Kminus;Lrpar;minus;0.045lpar;v1prime;minus;1rpar;rsqb;.This fits the spectrum in the observed range of quantum numbers,K= 11 to 20 andL = KtoK+8. The first two terms are associated with that prolate symmetrical top which comes closest to the actual ClO2molecule. Hence, neglecting the effect of asymmetry on the spectrum,2Dgr;Bmacr;equals;minus;lpar;0.0615plus;0.0042v1prime;rpar;thinsp;cmminus;1and2lpar;Dgr;Aminus;Dgr;Bmacr;rpar;equals;minus;lpar;1.188plus;0.008v1prime;rpar;thinsp;cmminus;1.The last term is associated with spin doubling. The coupling is shown to be close to Hund's ``caseb.'' The linear terms inLandKmay be a consequence of the doubling. The term inv1prime;Kdescribes an outstanding feature of the spectrum but is not interpreted. The bands are shown to be of the parallel type. A fewqPandqRbranches have also been identified and Dgr;1Fvalues have been found. Assuming the spectrum to be that of a prolate symmetrical top, the resulting values of 2Bmacr;for the vibrationless states are 2Bmacr;Prime; = 0.612 cmminus;1and 2Bmacr;prime; = 0.550 cmminus;1. The value of 2Bmacr;Prime; with the Clsngbnd;O distancesPrime; = 1.53A from electron diffraction is sufficient to determine the lower electronic state. The upper state is then determined from the values of 2Dgr;Bmacr;and 2(Dgr;Amdash; Dgr;Bmacr;) for the vibrationless states. The resulting model of both states is designated as model (2). Error in this model, because of the fact that the effect of asymmetry was neglected, is found to be small. Asymmetry correction made on model (2) leads to the following model:2thgr;prime;prime;equals;109compfn;plusmn;3compfn;,2thgr;prime;equals;92compfn;plusmn;6compfn;,thinsp;sprime;prime;equals;1.53Aplusmn;0.02A,thinsp;sprime;equals;1.805Aplusmn;0.05A.The rotational isotope effect is observed and explained but gives no additional information about the molecular model.