Chirped Pulse Fourier Transform Microwave Spectroscopy of SnCl Garry S. Grubbs II and Stephen A. Cooke Department of Chemistry, University of North Texas, 1155 Union Circle #305070, Denton, TX, USA,

Background Recently undertaken rotational studies of open-shell heavy metal containing molecules Computationally Complex Relativistic Complications Quadrupole Coupling and other constants give insight into bonding nature Larger implications

Previous Work Bandowski, Zyrnicki and Borkowska-Burnecka study on 120 Sn 35 Cl 1 Rotational band study in the UV region (0.05 cm -1 resolution) Constants given for ground and first vibrational states Zyrnicki gave a talk on this at this conference in N. Bandowski, W. Zyrnicki, and J. Borkowska-Burnecka, J. Phys. B: At. Mol. Phys., 20 (1987) 531.

Complexities Isotopes –10 isotopes of Tin –2 isotopes of Chlorine Nuclear Spin –Chlorine, I = 1.5 –Some Tin, I = 0.5 Electronic Spin –X 2 Π r SpeciesAbundanceNuclear Spin 112 Sn0.97 %0 114 Sn0.66 %0 115 Sn0.34 % Sn14.54 %0 117 Sn7.68 % Sn24.22 %0 119 Sn8.59 % Sn32.58 %0 122 Sn4.63 %0 124 Sn5.79 %0 35 Cl75.78 % Cl24.22 %1.5

Chirp Pulse Experiment Direct Digitization Circuit utilized Useful for giving accurate intensities for different isotopologues

Chirp Pulse Experiment To Diff. Pump Center Frequency, ν, between 8-18 GHz Linear Frequency Sweep 0 – x - “Chirp” ν +/- x is amplified, pulsed and broadcast Excitation interacts with the molecules Free Induction Decay Collected, Amplified and Digitized on a 40 GS/s oscilloscope

Cavity Experiment Circuit Design by J.-U. Grabow Nozzle introduced through the back of a mirror X

In Conjunction Uses Same Molecular Source 1 Idea is to use CP-FTMW and then use Cavity for a closer look. X 1. G. S. Grubbs II, C. T. Dewberry, K. C. Etchison, K. Kerr and S. A. Cooke, Rev. Sci. Instrum., 78 (2007)

Walker-Gerry Ablation Nozzle Similar to Smalley Nozzle

Experiment Chirp Pulse Experiment –Automated System –Averaged at least 50,000 FIDs when possible –1 GHz Scans Balle-Flygare type FTMW Experiment –Searched regions of dense spectra from CP-FTMW –Used extensively for help with GHz region

Notes 0.3% Gas Mix of Cl 2 in Ar Approximately 4.5 bar backing gas pressure bar Chamber Pressure 4 Hz Running Speed 3.5 μs Chirp Duration 500 MHz Chirp Width from Arbitrary Waveform Generator

Experiment Each 1 GHz scan ran for 10,000 FIDs Average five 10,000 FIDs to give 50,000 averages 40 μs FIDs used instead of typical 20 μs FID for 10 GHz scan 50 kHz spectral linewidths achieved AABS Package (Kisiel) 1 1. Z. Kisiel, L. Pszczolkowski, I. R. Medvedev, M. Winnewisser, F. C. De Lucia, C E. Herbst, J. Mol. Spectrosc., 233 (2005) 231.

Results J = 1.5 ← 0.5 transition Chirp Measurement: MHz FWHM: MHz J = 1.5 ← 0.5 transition Cavity Measurement: MHz FWHM: MHz

More Spectra

A Closer Look J = 2.5 ← 1.5 Transitions Chirp Measurement: MHz Chirp FWHM: MHz Cavity Measurement: MHz Cavity FWHM: MHz Chirp Measurement: MHz Chirp FWHM: MHz Cavity Measurement: MHz Cavity FWHM: MHz Chirp Measurement: MHz Chirp FWHM: MHz Cavity Measurement: MHz Cavity FWHM: MHz

Comparisons of eQq SpecieseQq 1 valueReference 12 C 35 Cl-34.26(13)1 28 Si 35 Cl-23.13(96)2 74 Ge 35 ClNo LiteratureN/A 120 Sn 35 ClNot Yet AvailableThis Work 208 Pb 35 Cl-24.94(7)See Talk RC07 (Cooke) Not Yet Assigned due to Complexities in the Hyperfine Splitting of the Molecule 1.N. Bandowski, W. Zyrnicki, and J. Borkowska-Burnecka, J. Phys. B: At. Mol. Phys., 20 (1987) K. Tanaka, H. Honjou, M. Tsuchiya, and T. Tanaka, J. Mol. Spectr., 251 (2008) 369.

Conclusions Pure Rotational Transitions of SnCl have been measured for the first time A Balle-Flygare FTMW type instrument has been used in conjunction with a CP-FTMW with a Laser Ablation Source Very accurate data but amount of data is finite at the moment

Future Work Use Cavity Experiment to locate more 120 Sn 35 Cl transitions Properly Assign Transitions Further experiments on GeCl (previously studied by Tanaka) 1 to lock down hyperfine structure and trends within the series Bromides, Fluorides, and Iodides 1. K. Tanaka, H. Honjou, M. Tsuchiya, and T. Tanaka, J. Mol. Spectrosc., 251 (2008) 369.

Acknowledgements Cooke Group (especially Rob and Brittany) Funding from the NSF and US DOE

Results Achieved using Pickett’s SPFIT/SPCAT software AABS Package

Magnetic Hyperfine Speciesa – (b+c)/2dReference 12 C 35 Cl93.9(22)82.212(37)1 28 Si 35 Cl49.84(73)46.40(94)2 74 Ge 35 ClNo Literature N/A 120 Sn 35 ClNot Yet Available This Work 208 Pb 35 Cl30.170(13) (55)See Talk RC07

120 Sn 35 Cl Constants ParameterLiterature 1 This Work B 0 /MHz (39) D 0 /kHz1.34 (4) p 0 /MHz (81) p D_0 /kHz A 0 /MHz (86940) A D_0 /MHz6.895 (120) a – (b+c)/2 /MHz d /MHz eQq 1 (Cl) /MHz

Tetrel Chlorides Have 2 Π r ground states Nuclear spin of chlorine increases assignment difficulty Spin-Orbit Constants TABLE