68 th International Symposium on Molecular Spectroscopy June

68 th International Symposium on Molecular Spectroscopy June 17 - 21, 2013 Millimeter and Sub-millimeter Spectroscopy of~ Cr. CCH (X 6Σ+) Jie Min and L. M. Ziurys Department of Astronomy Department of Chemistry and Biochemistry Steward Observatory University of Arizona

68 th International Symposium on Molecular Spectroscopy June 17 - 21, 2013 Importance of Metal Monoacetylides • Small transition metal organometallic radicals model systems • Examine fundamental interactions between metal and ligand • Test theoretical studies of bonding into d-shells • Metal (3 d) monoacetylide species of interest • MCCH fragments serve as intermediates in catalysis, synthesis • Limited spectroscopic information for 3 d Monoacetylies • Previous gas-phase spectroscopy: Cr. CCH (X 6Σ+): Electronic spectroscopy (R 2 PI) by Morse group (2004) Cu. CCH (X 1Σ+) & Zn. CCH (X 2Σ+): FTMW/mm-wave by Ziurys group (Sun et al. 2010; Min et al. 2012) • Examine periodic trends in 3 d MCCH series • Conduct mm-wave search for Cr. CCH

68 th International Symposium on Molecular Spectroscopy June 17 - 21, 2013 Millimeter-Wave Direct Absorption Study of Cr. CCH • Past mm-wave studies of Cu. CCH and Zn. CCH: VERY Difficult • Synthesis used Broida ovens; based on our FTMW data • Try different approach: Cr(CO)6 as chromium source • AC discharge in argon & HCCH • Velocity modulation spectrometer • Radiation Source: Gunn oscillators with Schottky diode multipliers (65 -660 GHz) • Reaction Chamber: Glass cell chilled by methanol • Gaussian beam optics • Detector: In. Sb bolometer • Source-modulation and detection at 2 f • Based on estimates of B, λ, γ (Morse)

68 th International Symposium on Molecular Spectroscopy June 17 - 21, 2013 • Raw Data: Search continuously over ~30 GHz 443000, 000 443500, 000 444000, 000 444500, 000 445000, 000 445500, 000 446000, 000 446500, 000 447000, 000 447500, 000 448000, 000 448500, 000 449000, 000 449500, 000 450000, 000 450500, 000 451000, 000 451500, 000 452000, 000 452500, 000 453000, 000 453500, 000 454000, 000 454500, 000 455000, 000 455500, 000 456000, 000 456500, 000 457000, 000 457500, 000 458000, 000 458500, 000 459000, 000 459500, 000 460000, 000 460500, 000 461000, 000 461500, 000 462000, 000 462500, 000 463000, 000 463500, 000 464000, 000 464500, 000 465000, 000 465500, 000 466000, 000 466500, 000 467000, 000 467500, 000 468000, 000 468500, 000 469000, 000 469500, 000 470000, 000 470500, 000 471000, 000 Pattern of Sextets emerged …

68 th International Symposium on Molecular Spectroscopy • Pure rotational data: exhibit sextets ~ Note weaker lines ! June 17 - 21, 2013

68 th International Symposium on Molecular Spectroscopy Confirmation with Cr. CCD • To confirm identification, searched for Cr. CCD • No previous constants, scaled from Cr. CCH constants • Method: Cr(CO)6 + DCCD in AC discharge • Five transitions measured, each consisting of sextets June 17 - 21, 2013

68 th International Symposium on Molecular Spectroscopy June 17 - 21, 2013 Current Spectroscopic Analysis • Fit 10 transitions of Cr. CCH (60 lines); 5 transitions of Cr. CCD (30 lines) • Improved constants, including all centrifugal distortion terms Parameter (MHz) Cr. CCH Cr. CCD Cr. CCH (Morse) B 3856. 0547(37) 3547. 0557(39) 3843 D 0. 00172314(50) 0. 00087661(45) -- γ 40. 703(28) 44. 849(31) 39. 6 γD -0. 1343(90) λ 8691 (21) 8672(26) 8703 λD -0. 003393(83) -0. 002968(85) rms 0. 091 0. 053 -- Heff = HRot + HSR + HSS • Searching for new transitions with FTMW system • Attempt 13 C substitution to establish a good structure --

68 th International Symposium on Molecular Spectroscopy June 17 - 21, 2013 Searches for Cr. C (X 3Σ-) • Based on Morse 2010 (B, γ, λ) • Searched over ~100 GHz on VM machine • Uncertainties in splittings • Cr(CO)6 + CH 4 in AC discharge J=N+1 J=N-1 J=NJ=N J=N+1 464074, 3 465074, 3 466074, 3 467074, 3 468074, 3 469074, 3 463674, 3 464674, 3 465674, 3 466674, 3 467674, 3 468674, 3 469674, 3 464174, 3 465174, 3 466174, 3 467174, 3 468174, 3 469174, 3 470174, 3 502541, 5 503041, 5503541, 5 504041, 5504541, 5 505041, 5505541, 5 506041, 5506541, 5 507041, 5507541, 5 508041, 5 508541, 5 503041, 5 504041, 5 505041, 5 506041, 5 507041, 5 508041, 5 509041, 5 541893, 3 542893, 3 543893, 3 544893, 3 545893, 3 546893, 3 541393, 3 542393, 3 543393, 3 544393, 3 545393, 3 546393, 3 547393, 3 541893, 3 542893, 3 543893, 3 544893, 3 545893, 3 546893, 3 547893, 3 J=N 464174, 3 465174, 3 466174, 3 467174, 3 468174, 3 469174, 3 470174, 3 503041, 4 504041, 4 505041, 4 506041, 4 507041, 4 508041, 4 541893, 4 542893, 4 543893, 4 544893, 4 545893, 4 546893, 4 547893, 4

68 th International Symposium on Molecular Spectroscopy J = N+1 J=N June 17 - 21, 2013 J = N-1 N = 11 → 10 425 427 429 N = 12 → 11 464 466 468 N = 13 → 12 503 505 507 509 N = 14 → 13 542 544 Frequency (GHz) 546

68 th International Symposium on Molecular Spectroscopy June 17 - 21, 2013 Preliminary Spectroscopic Analysis • Fit 7 transitions (three spin components each) of Cr. C in X 3Σ- state • Following effective Hamiltonian: Heff = HRot + HSR + HSS • Improved constants, including all centrifugal distortion terms Parameter (MHz) Cr. C (Morse) B 3856. 0547(37) 3843 D 0. 00182314(50) -- γ 46. 703(28) 39. 6 λ 8891 (21) 8703 λD -0. 003393(83) -- rms 0. 093 -- r 0 1. 631361 1. 61875

68 th International Symposium on Molecular Spectroscopy June 17 - 21, 2013 Results and Future Directions • First pure rotational study of Cr. CCH and Cr. C • Confirmed 6Σ and 3Σ ground electronic states, respectively • Monoacetylide: Spectra of Cr. CCD also measured • Searching for other isotopologues to establish structure (FTMW) • Cr. C: 13 C substitution • Other 3 d MCCH and MC species Funding: NSF