1. A NEW 2 Σ + - 2 Σ + TRANSITION OF PtF BY INTRACAVITY LASER ABSORPTION SPECTROSCOPY LEAH C O'BRIEN, TAYLOR DAHMS, KAITLIN A WOMACK Department of Chemistry, Southern Illinois University Edwardsville, IL JAMES J O'BRIEN Chemistry and Biochemistry, University of Missouri St. Louis, MO

2. Previous Work on PtF We reported ILS spectrum and analysis of the (0,0) and (1,0) bands of the [11.9] Ω= 3/2 - X 2 Π 3/2 transition of PtF J. Mol. Spectrosc. 265, 39-46 (2011) Bandheads at 11940 and 12496 cm -1 Microwave spectrum by Okabayashi et al. J. Chem. Phys. 136, 174311 (2012) Several older theoretical calculations on the ground state High level ab initio calculations Relativistic calculations on the low-lying 2 Π, 2 Δ, and 2 Σ states: Liu and Franke, J. Comp. Chem. 23, 564-575 (2002) PtF and HePtF calculations including relativistic effects: Zou, Liu, and Boggs, Dalton Trans. 39, 2023-2026 (2010).

3. Low-Lying States of PtF Ionic Molecule: Pt + (5d 9 )F – (2p 6 ) A SO = -4200 cm -1 Without Spin-Orbit With Spin-Orbit T e (eV)r e (Å) X 2 Π 3/2 0.0001.873 Ω=1/20.1061.894 2 Δ 5/2 0.1671.915 T e (eV)r e (Å) 2Σ2Σ0.0001.921 2Π2Π0.2521.913 2Δ2Δ 0.4621.942

4. Experimental Conditions Conditions same as previous PtF work; recorded at the same time as our previous work Produced in a Pt-lined hollow cathode plasma 0.35 to 0.60 Amp for discharge current ~1.6 Torr Argon support gas and trace amount of SF 6 Spectra recorded by Intracavity laser absorption spectroscopy, ILS T g ranged from 100 – 130 μs, pathlength ranged from 0.92 – 1.2 km Calibration based on spectra from external I 2 cell and Iodine Atlas Bandheads observed at 13078.9, 12523.4, and 11946.4 cm -1

5. Schematic of ILS Spectrometer

6. ILS Absorption spectrum of PtF

7. Vibrational Assignments Based on isotopologue structure, the band observed at 13078.9, 12523.4, and 11946.4 cm -1 were assigned as the (1,0), (0,0), and (0,1) bands, respectively. ΔG 1/2 ′ = 555.5 cm -1 ΔG 1/2 ″ = 577.0 cm -1

8. ILS Absorption spectrum of PtF

9. Rotational Analysis Four branches were observed in both the (0,0) and (1,0) bands Unusual spacing, considered 2 Σ - X 2 Π 3/2 Little overlap in J’s among the observed branches Method of combination differences not workable Set aside for several years Fall 2013 contacted by Wenli Zou with new calculations He suggested it might be a specific 2 Σ - 2 Σ transition Based on transition dipole moments, this is predicted to be strong transition in the vicinity of our spectral features

10. Ω = 1/2 and 3/2 Electronic States of PtF Wenli Zou, unpublished work, 2013

11. (V) 2 Σ + – A 2 Σ + transition No clear doublets → must have large γ values Try the Hougen method to estimate spin-rotation γ values (or λ-doubling p values) in Ω = ½ states of metal-halides with d 9 electron configuration NiCl NiF Predicted Atomic Energy Levels of a d 9 MX J.T. Hougen, J. Mol. Spectrosc. 267, 23– 35. (2011)

12. Predicting γ-Value for A 2 Σ + State Determine crystal field parameters C 0, C 2, and C 4 Need energies for each 2 Π, 2 Σ, and 2 Δ component: use data from Wenli Need A SO for Pt (5d 9 6s 1 ): known, A SO = -4210 cm -1 Estimate β: β ~ 0.89, and optimize Solve system of linear equations (used Wolfram Alpha) AβC0C0 C2C2 C4C4 -4210 cm -1 0.9004082.8613341

13. Identify Term Energies of States Associated with d 9 Electron Configuration One concern with applying Hougen method to PtF: low-lying quartet states may interfere with the X 2 Π, A 2 Σ +, and B 2 Δ states and invalidate the Hougen analysis

14. Predicting γ-Value for A 2 Σ + State Use A, β, C 0, C 2, and C 4 to calculate 2θ 2θ = 4.85 rads p/2B = -2.7 p = -1.48 cm -1 γ = +2.02 cm -1 NiF

15. PGopher Simulation using Predicted Molecular Constants for the (V) 2 Σ + – A 2 Σ + Transition RfRf PfPf ReRe PePe

16. Rotational Analysis Once we understood the spectrum, the analysis was straightforward Preliminary molecular constants are presented below EBD x 10 6 γγ D x 10 4 [12.5] 2 Σ +, v=1a + 13069.499(54)0.2370(46)9.3(23)0.52(10)-9.5(33) [12.5] 2 Σ +, v=0a + 12511.695(49)0.2426(46)9.1(23)0.50(10)-8.5(34) [12.5] 2 Σ +, calc 135690.2444 A 2 Σ +, v=0 a0.2690(41) 9.2(23) 1.85(85) -7.9(32) A 2 Σ +, calc79.0.27352.02

17. Summary The (0,0) and (1,0) bands of a new (V) 2 Σ + – A 2 Σ + transition have been analyzed Preliminary molecular constants obtained for both states Large values of γ High-level calculations from Wenli Zou very helpful Theoretical model from Jon Hougen invaluable Making progress on experimental observations of electronic structure of PtF

18. Potential Energy Curves for Ω= 1/2, 3/2, 5/2,7/2 and 9/2 states of PtF

19. Acknowledgements Funding from NSF SIUE Students: Taylor Dahms and Kaitlin Womack UMSL STARS (High School) Students: Meredith Redick and Rebecca Steinberg Wenli Zou (post-doc at Southern Methodist U) Jon Hougen Thank you for your attention!

21. MO Diagram for PtF d 9 electron configuration Low-lying 2 Π, 2 Σ, and 2 Δ states One concern with Hougen method: low-lying quartet states of PtF may interfere with the X 2 Π, A 2 Σ +, and B 2 Δ states and invalidate the Hougen analysis