1997
Longlived diatomic dications: Potential curves and radiative lifetimes for CaBr2+ and CaI2+ including relativistic effects
Publication
Publication
Molecular Physics , Volume 91  Issue 5 p. 777 787
Relativistic effective core potential calculations have been employed in the framework of a spinorbit configuration interaction to compute the lowestlying electronic states of the CaBr2+ and CaI2+ dications, and the results are compared with the data for the isovalent CaCl2+ system studied earlier. The ground X 2H state in all three dications arises from a strong polarization of X(2Po)(X = Cl, Br or I) by the Ca2+(1S) ion and is bound by 0·961·55 eV with respect to the corresponding diabatic dissociation limits. It is split by the spinorbit interaction into the X1 2Π3/2 and X2 2Π1/2 components, with the energy splittings calculated to be 647 cm1 (CaCl2+), 2115 cm1 (CaBr2+) and 3544cm1 (CaI2+). The X1 and X2 states are found to be thermodynamically stable in CaCl2+ and CaBr2+, while in CaI2+ the lowest dissociation limit, Ca+(2S) + I+(3P2), lies 1700 and 5200 cm1 lower than the X1 and X2 minima respectively. The X1 and X2 states in CaI2+ are extremely longlived, however, owing to the high and very broad potential barriers to dissociation. The first electronic excited state, A2Σ+, is also bound in all the above systems, although it is predissociated in CaBr2+ and CaI2+ at large internuclear distances. All other lowlying electronic states of CaX2+ are repulsive. Electricdipole moments are calculated for the A → X1,X2 transitions. The corresponding radiative lifetimes are found to be very long in CaCl2+: τ(A → X1) = 19·3 ms and τ(A → X2) = 9·9 ms (the values are given for v′ = 0), and become very significantly shorter for CaBr2+ and CaI2+ because of the stronger spinorbit interaction in the heavier systems. This effect is especially noticeable for the A → X2 transitions, for which the τ values are computed to be 364 μs in CaBr2+ and 50·3 us in CaI2+. The theoretical data obtained should aid in the future spectroscopic detection of these species. To data no experiment of this type has been successfully carried out for any of the thermodynamically stable diatomic dications.
Additional Metadata  

Molecular Physics  
Organisation  Department of Chemistry 
Alekseyev, A.B. (Aleksey B.), Liebermann, H.P. (HeinzPeter), Lingott, R. (Rainer), Buenker, R.J. (Robert J.), & Wright, J.S. (1997). Longlived diatomic dications: Potential curves and radiative lifetimes for CaBr2+ and CaI2+ including relativistic effects. Molecular Physics, 91(5), 777–787.
