No abstract

Electron spin resonance (ESR) studies are reported for Al16,17O, Ga16,17O, and In16,17O isolated in neon matrices at 4 K. Except for Al16O, no previous ESR measurements have been reported for these X 2Σ diatomic radicals. The pulsed laser vaporization of the metals in the presence of O162 and O172 produced high quality ESR spectra of these metal oxide radicals whose nuclear hyperfine interactions (A tensors) were fully resolved for both the metal and oxygen nuclei. An analysis of the experimental spin densities in combination with different types of theoretical calculations provided detailed information concerning the electronic structure trends going down this metal oxide group. Increased p-orbital spin density on oxygen was observed for the heavier metal oxide radicals. Nonrelativistic ab initio calculations with an extended basis set and the UB3LYP method reproduced the trends in the isotropic and dipolar hyperfine interactions. All-electron CI calculations, restricted open-shell Hartree–Fock (ROHF) wave functions, and unrestricted Hartree–Fock wave functions gave results very different from experiment and from each other for the isotropic interaction. All calculations were in fair agreement with each other for the dipolar interaction and provided an assignment of the sign for that term.

The ionization thresholds for the metastable Mg(3s3p 3P0)⋅RG(3Π0−,v′′=0) states (RG=Kr,Xe) have been determined by two-color photoionization via several Mg(3s4s 3S1)⋅RG(3Σ+,v′) intermediate resonance states. From other experimental measurements and ab initio calculations, D0(Mg(3s3p 3P0)⋅RG(3Π0−))=250±80 cm−1 and 500±150 cm−1 for RG=Kr,Xe, respectively, from which D0(MgKr+) and D0(MgXe+) are calculated to be 1891±80 cm−1 and 2848±150 cm−1. Bonding in the MgRG+ ions is discussed and compared to the bonding in the analogous NaRG+ and AlRG+ ions.

Mass-analyzed threshold ionization and structural isomers of M3O4 (M = Sc, Y, and La) J. Chem. Phys. 137, 084312 (2012); 10.1063/1.4747530 The interpretation of molecular magnetic hyperfine interactions J. Chem. Phys. 122, 084312 (2005); 10.1063/1.1851501 Ab initio and molecular-dynamics studies on rare gas hydrides: Potential-energy curves, isotropic hyperfine properties, and matrix cage trapping of atomic hydrogen The first nuclear hyperfine measurements of 17 O (Iϭ5/2) have been made for Sc 17 O, Y 17 O and La 17 O in their X 2 ⌺ ground electronic states. These metal oxide radicals were generated by the pulsed-laser vaporization of the metals in the presence of 16 O 2 / 17 O 2 and trapped in neon and argon matrices for electron spin resonance investigations. The fully resolved A tensors of the metal and 17O were compared with ab initio theoretical calculations-a comparison previously reported only for the ScO radical. The computational methods employed were unrestricted Hartree-Fock, density functional theory ͑DFT͒, and restricted open-shell Hartree-Fock. Having the metal and 17 O hyperfine interactions available has permitted a more thorough description of the electronic structure and charge distribution in these metal oxide molecules. An electronic structure comparison with the AlO, GaO, and InO radicals has also been made. Reasonably good agreement between the observed and calculated values of A iso and A dip were achieved with the DFT method providing the closest agreement.

The Cd⋅H2 and Cd⋅D2 van der Waals complexes were synthesized by expanding cadmium vapor and He/H2 mixtures into a supersonic free jet. The ‘‘half-collision’’ process, Cd(5s5p 1P1)⋅H2→Cd(5s5p 3PJ) +H2, was studied by fixing a probe dye laser pulse (delayed 10 ns) onto one of the Cd(5s6s 3S1←5s5p 3PJ) transitions while exciting the Cd⋅H2(Cd⋅D2) complex with a pump dye laser pulse tuned across frequencies near that of the free Cd(5s5p 1P1←5s5s 1S0) atomic transition. When the probe laser was tuned to detect Cd(5s5p 3P2), an action spectrum to the red of the atomic transition was obtained for Cd⋅H2 consisting of a broad continuum superimposed upon which was an anharmonic series of vibrational transitions with discernible, blue-shaded rotational structure. A similar spectrum was recorded for Cd⋅D2, except that only very broadened blue-shaded rotational structure was observed. From the isotopic band-head splittings, computer simulations of the rotational band structure, and recent ab initio calculations of Cd⋅H2 potential surfaces by Jack Simons and co-workers, it is tentatively concluded that the vibrational resonances are due to the (1B1;K′a=0) ←(1A1;K■a=1) perpendicular transition of ortho Cd⋅H2 (para Cd⋅D2 ). The continuum is assigned to the other perpendicular transitions of para and ortho Cd⋅H2(Cd⋅D2) which excite 1B2(K′a=0,1,2) and 1B1(Ka=1,2) states. The attractive 1B2 state predissociates rapidly due to potential surface crossings with both the 3A1 and 3B1 repulsive states of CdH2, and we postulate that the 1B1 energy levels with K′a≥1 are strongly coupled with the 1B2 levels with Ka≥1. The 1B1(K′a=0) level is predissociated via a less efficient surface crossing with the more strongly repulsive 3A1 state. The yield of Cd(5s5p 3P2) vs Cd(5s5p 3P1) for the ‘‘vibrational resonance’’ mechanism, 2.6±0.2, is quite different from that for the ‘‘continuum’’ mechanism, 1.17±0.05, consistent with this idea. The 3A1 state correlates only with Cd(5s5p 3P2), but the B2 spin–orbit component of the 3B1 state (which will be produced by predissociation of the 1B2 state) correlates with Cd(5s5p 3P1). We estimate that the CdH2(1B1) state has a value of De≊1700 cm−1 at R′e(Cd–H2)≊2.5 Å, qualitatively consistent with the ab initio calculations, which show that the CdH2(1B1) potential is quite flat, with no H–H bond stretching or appreciable repulsion until Cd–H2 distances as small as 2.0 Å are reached.