title: A correlated ab initio study of the A2 pi <-- X2 sigma+ transition in MgCCH.
abstract: The A2 pi <-- X2 sigma+ transition in MgCCH was studied with correlation consistent basis sets and single- and multireference correlation methods. The A2 pi excited state was characterized in detail; the x2 sigma+ ground state has been described elsewhere recently. The estimated complete basis set (CBS) limits for valence correlation, including zero-point energy corrections, are 22668, 23191, and 22795 for the RCCSD(T), MRCI, and MRCI + Q methods, respectively. A core-valence correction of +162 cm-1 shifts the RCCSD(T) value to 22830 cm-1, in good agreement with the experimental result of 22807 cm-1.
authors.affiliation: Molecular Research Institute, Palo Alto, CA 94304, USA. woon@hecla.molres.org
authors.forename: D E
authors.initials: DE
authors.lastname: Woon
mesh_terms: D055580:Astronomical Phenomena; D001256:Astronomy; D002244:Carbon / Q000737:chemistry; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003198:Computer Simulation; D004583:Electrons; D005609:Free Radicals; D008274:Magnesium / Q000737:chemistry*; D008433:Mathematics; D008958:Models, Molecular; D012984:Software
chemical_list: D005609:Free Radicals; D002244:Carbon; D008274:Magnesium