Spectroscopy of jethyphen;cooled AlMn and trends in the electronic structure of the 3dtransition metal aluminides

摘要

Jethyphen;cooled diatomic AlMn has been spectroscopically investigated and is shown to possess a5Pgr;iground state deriving from the Al (3s23p1,2P0)+Mn (3d54s2,6S) separated atom limit. This implies that the aluminum atom favors a 3ppgr; approach to the manganese atom, a result that is in agreement with previous studies on the related AlCa and AlZn molecules. The ground state bond length has been measured as 2.6384plusmn;0.0010 Aring;, a value which includes corrections due to spinndash;uncoupling effects in theXthinsp;5Pgr;istate. It is suggested that the5Pgr;istate emerges as the ground state due to a particularly favorable configuration interaction with a lowhyphen;lying5Pgr;istate that derives from the interaction of Al (3s23p1,2P0)+Mn lsqb;3d6(5D)4s1,6Drsqb;. Combination of the atoms in this excited state leads to a strong sgr;2covalent bond via a 3psgr;Alndash;4ssgr;Mninteraction, which causes this excited electronic state to drop in energy so that it is expected to lie within a few thousand cmminus;1of the ground electronic state. Following a discussion of the spectroscopic results on AlMn, an overall summary of the spectroscopic results on the 3dseries of transition metal aluminides is presented, along with predictions of the ground electronic states of the as yet unobserved AlSc, AlTi, and AlFe molecules.