Triplet states electronic, isoelectronic molecules

We estimate the relative term value for the a A state from that observed for PF (7090.41 cm" ). Relative terra values for the b E and A il states are estimated by analogy with those observed for PCI (6). As discussed by Coxon and Wickramaaratchi (6) for PCI, other singlet ( n) and triplet ( n and E) states may be expected to lie in the range 20000 - 35000 cm", similar to those observed for the isoelectronic molecules 0 , S2, and SO (2) Inclusion of estimated term values for these additional levels changes our entropy by only about 0.05 cal K mol at 4500 K, and we prefer to omit these levels at this time. The adopted electronic entropy contribution from the excited states amounts to 0.01 cal K" mol" at 1500 K, and this contribution increases to 0.51 cal ... 

---