63 rd International Symposium On Molecular Spectroscopy June

63 rd International Symposium On Molecular Spectroscopy June 18, 2008 Gas-Phase Rotational Spectrum Of HZn. CN (Χ 1Σ+) by Fourier Transform Microwave Techniques Ming Sun Aldo Apponi Lucy M. Ziurys Department of Chemistry Steward Observatory University of Arizona

63 rd International Symposium On Molecular Spectroscopy Introduction to Modern FTMW Spectrometer Gas phase: solvent Free studies Pure rotational transitions Transient species: radicals/ reaction intermediates Structures, Bond lengths can be precisely determined Electronic Properties Fine-Hyperfine structures Astrochemistry June 18, 2008

63 rd International Symposium On Molecular Spectroscopy June 18, 2008 Ziurys Group FTMW Spectrometer High Voltage B Solenoid Valve Top View + – E n 0 ± d Pulse Driver S 1 LNA 30 d. B S 2 D C A Mixer n 0 Coupler S 3 n 0 S 3 TTL Pulse Sequence Computer 4 -40 GHz LPF S 4 ±d A/D S 4 0 -50 d. B PIN Switch

63 rd International Symposium On Molecular Spectroscopy June 18, 2008 FTMW Spectrometer 20” mirrors (4 to 40 GHz operation) Complete computer control and tuning NI timing electronics and DAQ Modified FTMW++ (Jens Grabow) Two 8” gate valves for nozzle Radiation/magnetic shield planned 22” cryopump (14000 L/sec Ar) Linear Actuator Mirror sled Cryopump Nozzle w/ Dischage setup

63 rd International Symposium On Molecular Spectroscopy June 18, 2008 Spectroscopy of HZn. CN Transition Metal Cyanide MCN studied by Ziurys group Often radicals, including Zn. CN No studies of HMCN Production technique 0. 5% Zn(CH 3)2 + 0. 1% (CN)2 in 200 Psi Argon 1% D 2 added for DZn. CN Brewster and Ziurys, J. Chem. Phys. 117, 4853 (2002). Grotjahn, Brewster and Ziurys, J. Am. Chem. Soc. 124, 5895 (2002). Sheridan and Ziurys, J. Chem. Phys. 118, 6370 (2003).

63 rd International Symposium On Molecular Spectroscopy June 18, 2008 HZn. CN (Χ 1Σ+) … I 2 67 Zn: I = 5/2 14 N: I=1 D: I=1 H: I=1/2 I 1 J F Molecular axis H = Hrot + HQ + Hnsr Hrot = BJ 2 – DJ 4 HQ = ∆EQ(I, J, F)= Hnsr = ∑CI i Ii · J

63 rd International Symposium On Molecular Spectroscopy June 18, 2008

63 rd International Symposium On Molecular Spectroscopy June 18, 2008

63 rd International Symposium On Molecular Spectroscopy June 18, 2008

63 rd International Symposium On Molecular Spectroscopy June 18, 2008 Fitted Spectroscopic Constants for Isotopologues of HZn. CN (X 1Σ+). a Parameterb H 64 Zn. CN H 66 Zn. CN H 67 Zn. CN H 68 Zn. CN D 64 Zn. CN D 66 Zn. CN B 3859. 17616(47) 3830. 90806(47) D (KHz) 1. 1304(122) 1. 1161(122) 3817. 337468(283) 3804. 18983(47) 3722. 20564(39) 3697. 66702(40) 3817. 77804(71) 1. 1041(111) 1. 0978(122) 1. 0076(106) 0. 9952(110) 1. 1189(280) 0. 0816(127) 0. 0755(141) eq. Q(D) H 64 Zn 13 CN CI(N) (KHz) 1. 01(72) 0. 73(72) 1. 10(47) 0. 93(72) 1. 00(64) 0. 88(76) 0. 98(146) eq. Q(N) -5. 0901(44) -5. 0898(44) -5. 0896(47) -5. 0891(44) -5. 0899(37) -5. 0915 (42) -5. 0892(79) 0. 0007 0. 0009 0. 0006 0. 0003 CI(Zn) (KHz) 1. 623(265) eq. Q(Zn) -104. 5792(93) rms a b 0. 0003 0. 0010 Values in parentheses are 1 s errors. Values in MHz if not specified. 0. 0011

63 rd International Symposium On Molecular Spectroscopy June 18, 2008 Bond lengths for three Zinc species. a HZn. CN(Χ 1Σ+)b Zn. CN(Χ 2Σ+)c r 0 rs rm(1) r. HZn (Å) 1. 496 1. 497 1. 495 r. Zn. C (Å) 1. 901 1. 899 1. 897 1. 954 1. 952 1. 950 r. CN (Å) 1. 150 1. 148 1. 146 1. 143 1. 142 HZn. CH 3(Χ 1 A 1)d r 0 rs 1. 521 1. 928 Zn-C bond length: Radical vs Closed-shell: Zn. CN vs HZn. CN and HZn. CH 3 d-π* backbonding: HZn. CN vs HZn. CH 3 H-Zn bond length: d-π* backbonding causes electron density toward ligand Methyl Steric Hindrance Brewster and Ziurys, J. Chem. Phys. 117, 4853 (2002). J. B. Schilling, W. A. Goddard III and J. L. Beauchamp, J. Am. Chem. Soc. 108, 582 (1986).

63 rd International Symposium On Molecular Spectroscopy June 18, 2008 e. Qq values and related bond lengths of seven species. a HZn. C Nb e. Qq(D) (MHz) HZn. C H 3 c 0. 17 f 0. 08 e. Qq(67 Zn) (MHz) 104. 57 -109. 11 e. Qq(14 N) (MHz) 5. 09 r. H-X (Å) Zn. C CF 3 D CH 3 Zn. Fe N D 1. 495 DFj 0. 19 h 0. 35 -60 4. 93 b 1. 521 1. 091 1. 086 0. 92 g i 3 e. Qq(D) decreases w/ increasing bond length due to “s” orbital character 1. 928 Zn. CN 1. 76 1. 950 and are close r e. Qq(N) (Å) of HZn. CN 1. 897 d Zn-x 8 e. Qq(67 Zn) in both HZn. CN and 1. 142 HZn. CH 3 are large and indicates huge field r. C-N (Å) 1. 146 gradient across Zn nucleus d e. Qq(67 Zn) in HZn. CN is larger than that in Zn. F, which indicates large “p” orbital component

63 rd International Symposium On Molecular Spectroscopy June 18, 2008 Conclusion Linear Structure of HZn. CN was precisely determined. A relatively large e. Qq(67 Zn) value indicates a large electric field gradient across the zinc nucleus and thus high degree of covalent carbon-metal bonding. A relatively weak deuterium quadrupole coupling strength indicates a big H-metal distance.

63 rd International Symposium On Molecular Spectroscopy Acknowledgments • • Prof. Lucy Ziurys Dr. Aldo Apponi Rest of Ziurys Group members Engineers and Technicians in ARO • NSF • NASA June 18, 2008