Document Type


Publication Date

Spring 5-13-2013


Franck–Condon factors are investigated for sequences of free

main-group diatomic molecules. Theory-based Condon loci

(parabolas) and Morse-potential loci are plotted on Deslandres

tables to verify if they, indeed, follow the largest Franck–Condon

factors. Then, the inclination angles of the Condon loci

are determined. Thus, entire band systems are quantified by

one variable, the angle. For all available isoelectronic sequences,

this angle increases from a central minimum toward

magic-number molecular boundaries. The theory for the Condon

locus gives the angle in terms of the ratio of the upperstate

to the lower-state force constants. It is concluded that

the periodicity is caused due to the fact that this ratio

becomes larger as rare-gas molecules are approached, a trend

that probably points to the extreme cases of the rare-gas molecules

themselves. Thus, molecular periodicity echoes atomic

periodicity in that data plots have extrema at molecules with

magic-number atoms, yet it does not echo the details of

atomic periodicity in series between those molecules.