The vapor phase vacuum ultraviolet absorption spectra of methyl bromide, methylene bromide, bromoform, and carbon tetrabromide are reported for the region 40 000minus;90 000 cmminus;1(250minus;110 nm). Many of the Rydberg and intravalent absorptions of the bromine electrons in the nonbondingporbitals, which are perpendicular to the Cminus;Br bonding axes, and the sgr;ast;larr;sgr; (Cminus;Br) absorptions of the compounds have been assigned. A correlation of the molecular Rydberg series of methyl bromide to series in krypton, which has made possible the assignment of the 4dand 4fRydberg absorptions, is presented. Expanded vibrational progressions of the firstnsandnpRydberg transitions of methylbromide are presented. The analysis of these progressions indicates that transitions to the 5sand 5pRydberg orbitals bring about a Jahnminus;Teller distortion of the molecule. ThreensRydberg series of methylene bromide were assigned which converge on the ionization potentials of 10.629plusmn;0.010, 10.839plusmn;0.010, and 11.261plusmn;0.010 eV. The states formed upon ionization are assigned as theb2,b1, anda1, respectively, as thenstransitions of thea2combination of bromineporbitals are forbidden inC2vsymmetry. Other absorptions of methylene bromide, as well as the majority of the firstns,np, andndmolecular Rydberg assignments of bromoform and carbon tetrabromide were made using the term values of the bands with respect to the ionization potentials of the molecules. It was found that the averagednsterm values of the bromomethanes vary slightly through the series, while thenpterm values were increased in methylene bromide and bromoform. In each spectrum the assignment of the sgr;ast;larr;sgr; (Cminus;Br) bands was made based on an empirically derived relation.
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