Chirped Pulse Fourier Transform Microwave Spectroscopy of Sn

Chirped Pulse Fourier Transform Microwave Spectroscopy of Sn. Cl Garry S. Grubbs II and Stephen A. Cooke Department of Chemistry, University of North Texas, 1155 Union Circle #305070, Denton, TX, USA, 76203 -5017

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 1978 1. N. Bandowski, W. Zyrnicki, and J. Borkowska-Burnecka, J. Phys. B: At. Mol. Phys. , 20 (1987) 531.

Complexities Species • 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 Abundance Nuclear Spin 112 Sn 0. 97 % 0 114 Sn 0. 66 % 0 115 Sn 0. 34 % 0. 5 116 Sn 14. 54 % 0 117 Sn 7. 68 % 0. 5 118 Sn 24. 22 % 0 119 Sn 8. 59 % 0. 5 120 Sn 32. 58 % 0 122 Sn 4. 63 % 0 124 Sn 5. 79 % 0 35 Cl 75. 78 % 1. 5 37 Cl 24. 22 % 1. 5

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

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

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

In Conjunction • Uses Same Molecular Source 1 • Idea is to use CP-FTMW and then use Cavity for a closer look. 1. G. S. Grubbs II, C. T. Dewberry, K. C. Etchison, K. Kerr and S. A. Cooke, Rev. Sci. Instrum. , 78 (2007) 096106. X

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 16. 5 -17 GHz region

Notes • • • 0. 3% Gas Mix of Cl 2 in Ar Approximately 4. 5 bar backing gas pressure 10 -5 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 k. Hz 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 Cavity Measurement: 10069. 15959 MHz FWHM: 0. 007 MHz J = 1. 5 ← 0. 5 transition Chirp Measurement: 10069. 1555 MHz FWHM: 0. 0468 MHz

More Spectra

A Closer Look J = 2. 5 ← 1. 5 Transitions Chirp Measurement: 16903. 8529 16899. 3146 MHz 16902. 7336 Chirp FWHM: 0. 0845 0. 0903 MHz 0. 0883 Cavity MHz Cavity. Measurement: 16903. 87276 16902. 75093 16899. 3110 MHz Cavity FWHM: 0. 007 MHz 10899. 05 10899. 55

Comparisons of e. Qq Species e. Qq 1 value Reference 12 C 35 Cl -34. 26(13) 1 28 Si 35 Cl -23. 13(96) 2 74 Ge 35 Cl No Literature N/A 120 Sn 35 Cl Not Yet Available This Work 208 Pb 35 Cl -24. 94(7) See Talk RC 07 (Cooke) Not Yet Assigned due to Complexities in the Hyperfine Splitting of the Molecule 1. 2. N. Bandowski, W. Zyrnicki, and J. Borkowska-Burnecka, J. Phys. B: At. Mol. Phys. , 20 (1987) 531. K. Tanaka, H. Honjou, M. Tsuchiya, and T. Tanaka, J. Mol. Spectr. , 251 (2008) 369.

Conclusions • Pure Rotational Transitions of Sn. Cl 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 Ge. Cl (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 Species a – (b+c)/2 d Reference 12 C 35 Cl 93. 9(22) 82. 212(37) 1 28 Si 35 Cl 49. 84(73) 46. 40(94) 2 74 Ge 35 Cl No Literature N/A 120 Sn 35 Cl Not Yet Available This Work 208 Pb 35 Cl 30. 170(13) -40. 8326(55) See Talk RC 07

120 Sn 35 Cl Constants Parameter Literature 1 B 0 /MHz 3547. 14 (39) D 0 /k. Hz 1. 34 (4) p 0 /MHz -268. 6 (81) p. D_0 /k. Hz ----- A 0 /MHz 70704941. 99 (86940) AD_0 /MHz 6. 895 (120) a – (b+c)/2 /MHz ----- d /MHz ----- e. Qq 1(Cl) /MHz ----- This Work

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