Alkali triplet spectroscopy

The far quasistatically broadened wings of the Na D transition give important contributions to the emission and absorption spectrum of a high-pressure sodium discharge. We report experimental and theoretical spectra and discuss in particular the Na2 triplet satellite at 551.5 nm and the Na2 singlet satellite at 805 nm. Extension of this type of spectroscopy to other alkali metal vapors is discussed. 

Infrared spectroscopy in the CO stretching region provides a sensitive probe for detecting contact ion pair formation between cations and carbonylates (12,13). Good examples are provided by the early work on the interaction of cations with tetracarbonylcobaltate (12) and by more recent work on a variety of metal carbonyl anions (13,14). In solvents such as THF, alkali metal carbonylates appear to be present in two or three different forms tight (contact) ion pairs, looser ion pairs, and ion triplets. For example, Fig. 5 shows the IR spectrum of Na[Mn(CO)s] in THF and its deconvolution into two different sets of bands, which are associated with two different species in solution (14). For one of these the evidence points to a contact ion pair of structure 6. 

Generally the triplet ground state of alkali dimers is not directly accessible by absorption spectroscopy. Photo-association spectroscopy of cold colliding Li atoms wit a relative angular momentum / = 1 (/7-scattering) allows transitions from the state into an excited triplet state. Their measurements give precise values of high vibrational levels and allow the determination of the triplet potential. From measurements of rotational levels also the spin-spin and spin-rotation interaction can be deduced [620]. 

---