Fourier Transform Microwave Spectroscopy Of Sc13C2 and Sc12C13C: Establishing an Accurate Structure Of ScC2 (X2A1) ~ Sc C Mark A. Burton, DeWayne T. Halfen, Jie Min, and Lucy M. Ziurys Department of Chemistry and Biochemistry Department of Astronomy Arizona Radio Observatory University of Arizona

Importance of Dicarbides Delocalization of π-electrons causes the HOMO-LUMO gap to decrease with an increase carbons Doping changes electronic properties e- acceptors or donors Can change bandgap Great for photovoltaics La, Y, and Sc doped fullerenes Electronic studies on other metal and non-metal doped nanotubes (Marcos et al. 2003)

Endohedral Metallofullerene (EMF) (Wang et al. 2001) Endohedral Metallofullerene (EMF) ~ ~ YC2 (X2A1) and ScC2 (X2A1) are model systems Rayon et al. (1998) – DFT and CASSCF Nuclear spin yields magnetic hyperfine structure I(45Sc) = 7/2 I(13C) = 1/2 molecular bonding information Sc3N doped for artificial photosynthesis Sc4C2…just cool (Wang et al. 2013) (Rudolf et al. 2016)

F1 = J + I(45Sc) F = F1 + I(13C) I(45Sc) = 7/2 I(13C) = 1/2 NKa,Kc J 5 4 3 2 101 1/2 3/2 11/2 9/2 7/2 5/2 201 1 6 13/2 F1 = J + I(45Sc) F = F1 + I(13C) I(45Sc) = 7/2 I(13C) = 1/2 Sc13C2: N = 2 → 1 near 29.6 GHz F F1 NKa,Kc J 5 4 3 2 101 1/2 3/2 111 Sc C Itot(Sc12C2) = symmetric so only even rotational levels (i.e., Ka = 0, 2, 4, ...) exist All levels are allowed for Sc13C2 but even Ka levels are paired with Itot=0 so no F splittings seen Sc12C13C has no equivalent nuclei so all rotational levels are observed

Fourier Transform Microwave Spectrometer 2 sets of mirrors: 4 – 40 GHz (large) antenna 40 – 90 GHz (small) waveguide S1: Ar/13CH4 mix S2: DC discharge and short laser pulse – Sc rod S3: Microwave pulse S4: Detection Detected by Low Noise Amplifier (Sun et al. 2009)

Antenna imbedded in mirror used as microwave source Motor Metal Rod Holder Teflon Nozzle - Discharge Pulsed Valve Laser Path Rotating/Translating Apparatus Gaseous Mixture Antenna imbedded in mirror used as microwave source Antenna collects emitted frequencies Nd/YAG laser at 532 nm Ablation adapter with Teflon nozzle Added 0.5% 13CH4 in Argon DC discharge at 800 Volts Laser Beam Internal window

Observed Sc13C2 Transitions SHOTS 2000 5000 2000 5000

Running From the Mold

Data Thus Far Sc13C2 Observed Transition Frequencies with Preliminary Assignment Nka,Kc’ → Nka,Kc’’ J’ → J’’ F’ → F’’ νobs (MHz) 101 → 000 1 → 1 4 → 3 14803.456 2 → 1 3 → 3 14856.053 5 → 4 14870.465 202 → 101 2 → 3 29600.227 2 → 2 4 → 4 29634.981 3 → 2 29651.205 29671.460 29672.030 6 → 5 29696.930 Sc12C13C Observed Transition Frequencies Nka,Kc’ → Nka,Kc’’ νobs (MHz) 101 → 000 15244.331 15245.306 15260.264 202 → 101 30331.504 30347.971 30385.495 30409.065 30410.216

Preliminary Rotational Parameters Sc12C2a (MHz) Sc13C2 (MHz) Theoryb (MHz) A 53000c 51787 53000 B 8421.1313(24)d 7981 8390 C 7271.4184(21) 6863 7240 DN 0.10612(25) 0.10612 DNK 1.5 HN 6.71(77) x 10-5 6.7124 x 10-5 εbb + εcc 149.048(25) ΔSN 0.27484(53) aF 1305(11) 731.30 aFD 0.00191(82) 0.001914 Taa 37.054(58) 55 TaaD 0.713(30) Tbb - Tcc -193.9(9.7) χaa 49.469(61) rms 0.006 a: Min et al. 2014 b: calculated from the structure given in Rayon & Largo 2006 c: held fixed d: ratio held fixed

To Do/Future Experiments Finish putting lab together Search for more Sc13C2 and Sc12C13C lines More accurate structure TiC2 Rayon et al. – 1998 Predicted cyclic/triangular C2v 3B2 ground state Sumathi & Hendrickx – 1998 cyclic 3B1 ground state

Acknowledgements Dr. Lucy Ziurys Dr. DeWayne Halfen Dr. Jie Min Kyle Kilchenstein John Keogh Deborah Schmidt NSF, NASA, and University of Arizona

YC2 and Isotopologues - I(89Y) = 1/2 101 55 101 42 94 52 94 41

Observed Sc13C2 Transitions - I(45Sc) = 7/2 et. al et. al

Fourier Transform Microwave (FTMW) Carrier Gas Laser Pulse Poppet Sample Rod Low Noise Amplifier Computer Pulsed Valve figure modified from: Sun, M.; Halfen, D. T.; et. al. The Rotational Spectrum of CuCCH: A Fourier Transform Microwave Discharge Assisted Laser Ablation Spectroscopy and Millimeter/Submillimeter Study. J. Chem. Phys, 2010, 133, 174301