Transcript IrSi 4.pptx
The 68th International Symposium on Molecular Spectroscopy, June 2013 The electric dipole moment of Iridium monosilicide, IrSi Anh T. Le and Timothy C. Steimle Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287 Michael D. Morse and Maria A. Garcia Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA Lan Cheng and John F. Stanton Funded by DoE-BES The University of Texas at Austin, Austin, TX 78712-0165. Motivation Iridium containing molecules • IrSi? Previous work •Prof Morse’s group: Recorded 31 electronic bands * Recorded high resolution LIF of the (6,0)[16.0]1.5 - X2D5/2 bands for 191&193IrSi (lowest angular momentum quantum number) Analyzed, determined the fine and hyperfine parameters Recorded & Analyzed Stark spectra to determine the molecular dipole moments for the X2D5/2 and [16.0]1.5(v=6) states Experiment method Ablation laser Gated photon counter Skimmer Stark Plates Well collimated molecular beam Rot.Temp.<20 K Electric field ~ 4000 V/cm Resolution ~30 MHz CW dye laser Observation (6,0)[16.0]1.5-X2D5/2 band Complicated spectrum Large isotopic shifts (1.5cm-1) between 191IrSi, 193IrSi Formed a head quickly due to large difference in rotational constants Highly overlapped Need to understand the field free spectrum to be able to study the Stark spectra Observation (cont.) (6,0)[16.0]1.5-X2D5/2 band Resolution ~30 MHz Modeling the (6,0)[16.0]1.5-X2D5/2 band system 1. Effective Hamiltonian Heff = Hso+ Hrot + Hmhf(Ir)+ HeQq(Ir) Ir(I=3/2) 2. 16x16 Matrix representation: Hund’s case (abJ) coupled basis set: Eigenvalues & Eigenvectors Parameters: B, h5/2(191,193Ir) and eQq0(191,193Ir) for the X2D5/2(v=0) state,T00, B, h3/2(191,193Ir) and eQq0(191,193Ir) for the (6,0)[16.0]1.5 Predicted spectra Stark effect (next slide) Ready for Stark measurement & analysis P(5/2) under applied electric field 2339 V/cm|| LIF signal 1754 V/cm|| 1169 V/cm|| 0V/cm 191P(11/2) Facing the Challenge •9 field free transitions in P(5/2) splits into ~30 intense DMJ= DMF transitions, and numerous weaker DMJ DMF transitions under applied electric field •Fully resolved at voltage higher than 4000V/cm (impossible) What to expect? 1. Comparison with isovalent IrC m(X2D5/2)=1.60(7) D Expect small positive dipole moment 2. Electronegativity Si (8.15eV)<Ir (9.0eV) Possible to have small negative dipole moment Stark spectra of IrSi Predicted spectra C,D AB 1754 V/cm|| c b a A B C D LIF signal a b c 193IrSi, P(5/2) Predicted spectra LIF signal m(X2D5/2)=+0.414(6)D m([16.0]1.5(v=6))=-0.782(6)D m(X2D5/2)=-0.414 (6)D m([16.0]1.5(v=6))=0.782(6)D Difference in bonding IrSi and IrC Si (8.15eV) IrSi: Covalent bond Ir (9.0eV) C (11.25eV) IrC: Ionic bond Compare with other Ir - containing molecule Predict the reduced dipole moment of other Ir-containing molecule • • IrP • IrS IrCl • IrO Summary Recorded high resolution LIF of the (6,0)[16.0]1.5 - X2D5/2 bands for 191&193IrSi Analyzed, determined the fine and hyperfine parameters Recorded & Analyzed Stark spectra to determine the molecular dipole moments for the X2D5/2 and [16.0]1.5(v=6) states High level relativistic calculations are in good agreement with observed dipole moment and eQq0 (mag. hyperfine?) Compared reduce dipole moment of other Ir-containing molecules with IrSi Predict the reduced dipole moment of other Ir-containing molecule Thank you Advisor: Prof. Timothy C. Steimle Collaborations: Prof. Michael Morse (University of Utah) –IrSi Prof. John Stanton, Dr. Lan Cheng (U.Texas-Austin) -IrSi Group members: Fang Wang Ruohan Zhang Funding sources: DoE-BES Stark spectra of IrSi Determined Isovalent IrC dipole moments of IrSi m(X2D5/2)=-0.4139(64) D Comparison m(X2D5/2)=1.60(7) D m([16.0]1.5(v=6))=0.7821(63) D X2D5/2 : 12 14 22 13 32 X2D5/2 : 12 14 22 1332 Why? next slide