Chirped-Pulse Microwave Spectroscopy in the Undergraduate Chemistry Curriculum Sydney Gaster, Taylor Hall, Sean Arnold, Deondre Parks, Gordon Brown Department of Science and Mathematics Coker College, Hartsville, SC, USARC07

Microwave Spectroscopy at Coker College Coker College’s CP-FTMW spectrometer FTMW spectroscopy in a teaching laboratory FTMW spectroscopy in undergraduate research 2

3 Spectrometer Diagram 1 GHz Chirped Pulse Analog Devices frequency ranges (4 - 8 and GHz) MW Synthesizer (4 GHz ref) 10 W

4 Chirped Pulse Microwave Spectrometer

DDS vs. AFG Tektronix AFG3251 Analog Devices 9914 Bandwidth240 MHz2000 MHz Price$8,230$600 ISMS 2013 WH07: Ian Finneran, Daniel Holland, Brandon Carroll, Geoffrey Blake, California Institute of Technology, Rev. Sci. Instrum. 84, (2013)

6 Tektronix AFG3251 : Analog Devices 9914 :

MULTI-PULSE EXPERIMENTS

Room-Temp Spectrometer 9

Microwave Spectroscopy at Coker College Coker College’s CP-FTMW spectrometer FTMW spectroscopy in a teaching laboratory FTMW spectroscopy in undergraduate research 10

Step 1: ab initio Calculation 11

Step 2: Measure Spectrum 12

Step 3: Assign Spectrum 13 ISMS 2013 WH06: A.J. Minei, S.A. Cooke, Pure Rotational Spectroscopy of Asymmetric Tops in the Undergraduate Classroom or Laboratory. (2013);

Step 3: Assign Spectrum 14

Step 3: Assign Spectrum 15

Microwave Spectroscopy at Coker College Coker College’s CP-FTMW spectrometer FTMW spectroscopy in a teaching laboratory FTMW spectroscopy in undergraduate research 16

17 Objectives for this Research: Measure and assign the rotational spectrum of 3-iodopyridine Test case: Does the Coker CP-FTMW spectrometer have sufficient resolution to measure two quadrupolar nuclei? 3-iodopyridine

18 Experimental Spectrum of 3-iodopyridine Measured with AFG3252 – 43 x 250 MHz steps 10,000 signal averages (approximately 40 hours of measurement time) Valve Conditions: Backing Pressure set to 60 psi Nozzle heated to ~95° C

19 Experimental Spectrum of 3-iodopyridine Measured with AFG3252 – 43 x 250 MHz steps 10,000 signal averages (approximately 40 hours of measurement time) Valve Conditions: Backing Pressure set to 60 psi Nozzle heated to ~95° C

20 Experimental Spectrum of 3-iodopyridine Measured with ad x 1000MHz steps 10,000 signal averages (approximately 10 hours of measurement time) Valve Conditions: Backing Pressure set to 50 psi Nozzle heated to ~95° C

21 Experimental Spectrum of 3-iodopyridine Measured with ad x 1000MHz steps- 10 MW pulses for each valve pulse 10,000 signal averages (approximately 1.5 hours of measurement time) Valve Conditions: Backing Pressure set to 50 psi Nozzle heated to ~95° C

22 Experimental Spectrum of 3-iodopyridine (Low Frequency Graph) 10,000 signal averages (approximately 7 hours of measurement time) Nozzle Conditions: Backing Pressure set to 50 psi Nozzle heated to ~95° C

23 Line Assignments using AABS Software: Z.Kisiel, in: J.Demaison et al. (Eds.), Spectroscopy from Space, Kluwer Academic Publishers, Dordrecht, 2001, pp

24 Line Assignments using AABS Software:

Table 1: Experimental Rotational Constants Rotational Parameters 3-iodopyridine B3LYP/ 6 ‑ 311++g(d,p) Experimental A (MHz) (2) B (MHz) (8) C (MHz) (6) 3/2 Χ aa N(MHz) (1) ¼ Χ bb – Χ cc N(MHz) (2) Χ ab N(MHz) (2) 3/2 Χ aa I(MHz) (1) ¼ Χ bb – Χ cc I(MHz) (2) Χ ab I(MHz) (2) Number of Assigned Lines N/A213 OMC (MHz) N/A Inertial Defect (amu*A 2 ) (1) Rotational and Quadrupole Coupling Constants 25

Conclusions: Developed CP-FTMW instrumentation for undergraduate institution Implemented microwave spectroscopy in a classroom setting Measured and assigned GHz spectrum of 3-iodopyridine 3-iodopyridine 26

Acknowledgements South Carolina Independent Colleges and Universities Student-Faculty Research Program National Science Foundation (CHE ) Coker College 27