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

2. June 17- 21, 2013 68 th International Symposium on Molecular Spectroscopy Importance of Metal Monoacetylides Small transition metal organometallic radicals model systems Examine fundamental interactions between metal and ligand Test the theoretical studies of bonding into d-shells Metal (3d) monoacetylide species of interest MCCH fragments serve as intermediates in catalysis, synthesis Limited spectroscopic information for 3d Monoacetylies Previous gas-phase spectroscopy: CrCCH (X 6 Σ + ): Electronic spectroscopy (R2PI) by Morse group (2004) CuCCH (X 1 Σ + ) & ZnCCH (X 2 Σ + ): FTMW/mm-wave by Ziurys group (Sun et al. 2010; Min et al. 2012) Examine periodic trends in 3d MCCH series Conduct mm-wave search for CrCCH

3. June 17- 21, 2013 68 th International Symposium on Molecular Spectroscopy Past mm-wave studies of CuCCH and ZnCCH: 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: InSb bolometer Source-modulation and detection at 2f Based on estimates of B, λ, γ (Morse) Millimeter-Wave Direct Absorption Study of CrCCH

4. June 17- 21, 2013 68 th International Symposium on Molecular Spectroscopy Raw Data: Search continuously over ~30 GHz Pattern of Sextets emerged …

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

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

7. June 17- 21, 2013 68 th International Symposium on Molecular Spectroscopy Parameter (MHz)CrCCHCrCCDCrCCH (Morse) B3856.0547(37)3547.0557(39)3843 D0.00172314(50)0.00087661(45)-- γ40.703(28)44.849(31)39.6 γDγD -0.1343(90) λ8691 (21)8672(26)8703 λDλD -0.003393(83)-0.002968(85)-- rms0.0910.053-- Searching for new transitions with FTMW system Attempt 13 C substitution to establish a good structure Current Spectroscopic Analysis H eff = H Rot + H SR + H SS Fit 10 transitions of CrCCH (60 lines); 5 transitions of CrCCD (30 lines) Improved constants, including all centrifugal distortion terms

8. June 17- 21, 2013 68 th International Symposium on Molecular Spectroscopy J=N J=N+1 J=N-1 J=NJ=N-1J=N+1 J=NJ=N-1 J=N+1 Searches for CrC (X 3 Σ - ) Based on Morse 2010 (B, γ, λ) Uncertainties in spin splittings Searched over ~100 GHz on VM machine Cr(CO) 6 + CH 4 in AC discharge

9. June 17- 21, 2013 68 th International Symposium on Molecular Spectroscopy J = N+1 J = NJ = N-1 N = 11 10 N = 12 11 N = 13 12 N = 14 13 Frequency (GHz)

10. June 17- 21, 2013 68 th International Symposium on Molecular Spectroscopy Parameter (MHz)CrCCrC (Morse) B3856.0547(37)3843 D0.00182314(50)-- γ46.703(28)39.6 λ8891 (21)8703 λDλD -0.003393(83)-- rms0.093-- r0r0 1.6313611.61875 Fit 7 transitions (three spin components each) of CrC in X 3 Σ - state Following effective Hamiltonian: H eff = H Rot + H SR + H SS Improved constants, including all centrifugal distortion terms Preliminary Spectroscopic Analysis

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