title: The pure rotational spectra of the open-shell diatomic molecules PbI and SnI.
abstract: Pure rotational spectra of the ground electronic states of lead monoiodide and tin monoiodide have been measured using a chirped pulsed Fourier transform microwave spectrometer over the 7-18.5 GHz region for the first time. Each of PbI and SnI has a X (2)Π1/2 ground electronic state and may have a hyperfine structure that aids the determination of the electron electric dipole moment. For each species, pure rotational transitions of a number of different isotopologues and their excited vibrational states have been assigned and fitted. A multi-isotopologue Dunham-type analysis was carried out on both species producing values for Y01, Y02, Y11, and Y21, along with Λ-doubling constants, magnetic hyperfine constants and nuclear quadrupole coupling constants. The Born-Oppenheimer breakdown parameters for Pb have been evaluated and the parameter rationalized in terms of finite nuclear field effects. Analysis of the bond lengths and hyperfine interaction indicates that the bonding in both PbI and SnI is ionic in nature. Equilibrium bond lengths have been evaluated for both species.
authors.affiliation: Department of Chemistry, University of Leicester, Leicester LE1 7RH, United Kingdom.
authors.forename: Corey J
authors.initials: CJ
authors.lastname: Evans
authors.affiliation: Department of Chemistry, University of Leicester, Leicester LE1 7RH, United Kingdom.
authors.forename: Lisa-Maria E
authors.initials: LM
authors.lastname: Needham
authors.affiliation: School of Chemistry, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom.
authors.forename: Nicholas R
authors.initials: NR
authors.lastname: Walker
authors.affiliation: School of Chemistry, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom.
authors.forename: Hansjochen
authors.initials: H
authors.lastname: Köckert
authors.affiliation: School of Chemistry, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Zaleski
authors.affiliation: School of Chemistry, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom.
authors.forename: Susanna L
authors.initials: SL
authors.lastname: Stephens