June 17- 21, 2013 68th International Symposium on Molecular Spectroscopy

Millimeter and Sub-millimeter Spectroscopy of CrCCH (X 6Σ+)

Jie Min and L.M. ZiurysDepartment of Astronomy

Department of Chemistry and BiochemistrySteward ObservatoryUniversity of Arizona

~

371.64 371.67 371.70

CaC (X3 ): N = 17 18

Frequency (GHz)

J = 17 18J = 18 19J = 16 17

June 17- 21, 2013 68th 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 (X6Σ+): Electronic spectroscopy (R2PI) by Morse group (2004)

CuCCH (X1Σ+) & ZnCCH (X2Σ+): 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 CrCCHCu C C H

1.8177 Å 1.2174 Å 1.046 Å

June 17- 21, 2013 68th 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

June 17- 21, 2013 68th International Symposium on Molecular Spectroscopy

443000.000 443500.000 444000.000 444500.000 445000.000 445500.000 446000.000 446500.000 447000.000

447000.000 447500.000 448000.000 448500.000 449000.000 449500.000 450000.000 450500.000 451000.000

451000.000 451500.000 452000.000 452500.000 453000.000 453500.000 454000.000 454500.000 455000.000

455000.000 455500.000 456000.000 456500.000 457000.000 457500.000 458000.000 458500.000 459000.000

459000.000 459500.000 460000.000 460500.000 461000.000 461500.000 462000.000 462500.000 463000.000

463000.000 463500.000 464000.000 464500.000 465000.000 465500.000 466000.000 466500.000 467000.000

467000.000 467500.000 468000.000 468500.000 469000.000 469500.000 470000.000 470500.000 471000.000

• Raw Data: Search continuously over ~30 GHz

Pattern of Sextets emerged …

June 17- 21, 2013 68th International Symposium on Molecular Spectroscopy

468.00 468.05 468.10 468.15 468.20 468.25

460.35 460.40 460.45 460.50 460.55 460.60

475.65 475.70 475.75 475.80 475.85

CrCCH (X 6+)~

Frequency (GHz)

N = 60 59J = 57.5 56.5

J = 58.5 57.5 J = 59.5 58.5 J = 60.5 59.5J = 61.5 60.5 J = 62.5 61.5

N = 61 60J = 58.5 57.5 J = 59.5 58.5 J = 60.5 59.5

J = 61.5 60.5

J = 62.5 61.5J = 63.5 62.5

N = 62 61J = 59.5 58.5 J = 60.5 59.5J = 61.5 60.5

J = 62.5 61.5J = 64.5 63.5

J = 63.5 62.5N = 59

N = 60

56.5

57.5

58.5

59.5

60.561.5

srHssH

57.5

58.5

59.5

60.5

61.562.5

N = J = +1

rotH

CrCCH (X 6+)

J

~

• Pure rotational data: exhibit sextets

Note weaker lines !

June 17- 21, 2013 68th International Symposium on Molecular Spectroscopy

451.60 451.65 451.70 451.75 451.80 451.85

CrCCD (X 6+)~

Frequency (GHz)

N = 64 63

J = 61.5 60.5J = 62.5 61.5

J = 63.5 62.5 J = 64.5 63.5J = 65.5 64.5

J = 66.5 65.5

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

June 17- 21, 2013 68th International Symposium on Molecular Spectroscopy

Parameter (MHz) CrCCH CrCCD CrCCH (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 --

• Searching for new transitions with FTMW system

• Attempt 13C substitution to establish a good structure

Current Spectroscopic Analysis

Heff = HRot + HSR + HSS

• Fit 10 transitions of CrCCH (60 lines); 5 transitions of CrCCD (30 lines)

• Improved constants, including all centrifugal distortion terms

June 17- 21, 2013 68th International Symposium on Molecular Spectroscopy

4641

74.3

33

4651

74.3

33

4661

74.3

33

4671

74.3

33

4681

74.3

33

4691

74.3

33

4701

74.3

33

503041.381 505041.381 507041.381 509041.381

541893.4 542893.4 543893.4 544893.4 545893.4 546893.4 547893.4

J=N

463674.3357 465674.3357 467674.3357 469674.3357

502541.5041 504541.5041 506541.5041 508541.5041

541393.3061 543393.3061 545393.3061 547393.3061

J=N J=N+1J=N-1

503041.5041 505041.5041 507041.5041 509041.5041

464174.3357 466174.3357 468174.3357 470174.3357

541893.3061 543893.3061 545893.3061 547893.3061

J=NJ=N-1 J=N+1J=N

464074.2971 466074.2971 468074.2971 470074.2971

503041.4622 505041.4622 507041.4622 509041.4622

5418

93.2

61

5428

93.2

61

5438

93.2

61

5448

93.2

61

5458

93.2

61

5468

93.2

61

5478

93.2

61

J=N-1 J=N+1

Searches for CrC (X3Σ-)

• Based on Morse 2010 (B, γ, λ)

• Uncertainties in spin splittings

• Searched over ~100 GHz on VM machine

• Cr(CO)6 + CH4 in AC discharge

June 17- 21, 2013 68th International Symposium on Molecular Spectroscopy

J = N+1 J = N J = N-1

N = 11 → 10

N = 12 → 11

N = 13 → 12

N = 14 → 13

Frequency (GHz)

464 466 468 470

425 427 429 431

503 505 507 509

542 544 546 548

CrC (X 3-)

546.22543.24 544.90

464.88 467.17 468.91

N = 12 11J = 11 10 J = 12 11 J = 13 12

J = 11 10

504.10 506.04 507.55

N = 13 12

J = 12 11 J = 13 12 J = 14 13

N = 14 13

J = 13 12 J = 14 13 J = 15 14

Frequency (GHz)

June 17- 21, 2013 68th International Symposium on Molecular Spectroscopy

Parameter (MHz) CrC CrC (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 --

r0 1.631361 1.61875

• Fit 7 transitions (three spin components each) of CrC in X 3Σ- state

• Following effective Hamiltonian: Heff = HRot + HSR + HSS

• Improved constants, including all centrifugal distortion terms

Preliminary Spectroscopic Analysis

June 17- 21, 2013 68th International Symposium on Molecular Spectroscopy

First pure rotational study of CrCCH and CrC

Confirmed 6Σ and 3Σ ground electronic states, respectively

Monoacetylide: Spectra of CrCCD also measured

Searching for other isotopologues to establish structure (FTMW)

CrC: 13C substitution

Other 3d MCCH and MC species

Results and Future Directions

Funding: NSF