1. 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

2. 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)

3. 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)

4. 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

5. 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)

6. 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

7. Observed Sc13C2 Transitions
SHOTS
2000
5000
2000
5000

8. Running From the
Mold

9. 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
2 → 1
3 → 3
5 → 4
202 → 101
2 → 3
2 → 2
4 → 4
3 → 2
6 → 5
Sc12C13C Observed Transition Frequencies
Nka,Kc’ → Nka,Kc’’
νobs (MHz)
101 → 000
202 → 101

10. Preliminary Rotational Parameters
Sc12C2a (MHz)
Sc13C2 (MHz)
Theoryb (MHz) A
53000c
51787
53000 B
(24)d
7981
8390 C
(21)
6863
7240 DN
(25)
DNK
1.5 HN
6.71(77) x 10-5
x 10-5
εbb + εcc
(25)
ΔSN
(53) aF
1305(11)
731.30
aFD
(82)
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

11. 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

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

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

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

16. 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,