June 21, 201166th International Symposium on Molecular Spectroscopy

Fourier-Transform Microwave Spectroscopy of FeCN (X4Di): Confirmation of the Ground

Electronic State

Lindsay N. Zack, Jie Min, Brent J. Harris, Michael A. Flory, and Lucy M. Ziurys

Department of Chemistry and Biochemistry, Department of Astronomy and Steward Observatory, University of Arizona

June 21, 201166th International Symposium on Molecular Spectroscopy

Importance of Metal Cyanides

• Metals bonded to CN moiety found in many areas of chemistry• Biochemistry (e.g. Vitamin B-12: Co-CN bonds)• Pigments (e.g. Prussian Blue: Fe-CN and Fe-NC bonds)

• Also important in astrophysics• Most common metal carriers in interstellar gas (MgNC, MgCN, AlNC, NaCN,

KCN identified in several C-rich envelopes)

• Spectroscopically: Three different structures

NM C CNM

C N

M

Alkali-earth/main group M = Ca, Mg, Al, Ga, In(also predicted for early 3d metals)

Transition metalsM = Cr, Co, Ni, Cu, Zn

Alkali metalsM = Na, K

LINEAR CYANIDE

T-SHAPED

LINEAR ISOCYANIDE

June 21, 201166th International Symposium on Molecular Spectroscopy

Previous Work on FeNC/FeCN• Laser Fluorescence Spectroscopy (Lie & Dagdigian 2001)

• Observed W = 7/2′ ← W″ = 9/2 transition of FeN12C and FeN13C• Proposed 6D ground state; same as FeF and FeCl

• Theoretical Calculations (DeYonker et al. 2004; Hirano et al. 2006, 2007; Redondo et al. 2010)

• Several levels of theory• Disagree on lowest energy isomer (FeCN vs. FeNC); agree on 6D

ground state

A bit confusing !!! Who is correct ??

• Rotational Spectroscopy (Flory & Ziurys)

• Observed several rotational transitions• FeCN lowest in energy• Proposed 4Di ground state; same

as FeH • Also measured W = 9/2 ladder of

FeNC (X6Di)

June 21, 201166th International Symposium on Molecular Spectroscopy

4Di

W 1/23/25/27/2

13/2

11/2

9/2

7/2

J

9/2

7/2

5/2

11/2

9/2

7/2

5/2

3/2

1/2

7/2

5/2

3/2

6Di

W 1/23/25/27/2

13/2

11/2

9/2

7/2

J

9/2

7/2

5/2

11/2

9/2

7/2

5/2

3/2

1/2

7/2

5/2

3/2

15/2

13/2

11/2

9/2

9/2

1/2

7/2

5/2

3/2

-1/2

Energy Level Diagrams: 4Di vs. 6Di

= + , … , -W L S L S

Lowest transition J = 9/2 7/2 Lowest transition J = 11/2 9/2

June 21, 201166th International Symposium on Molecular Spectroscopy

Lowest transition for 4Di

J = 9/2 7/2

n ~ 36100 MHz (based on Flory’s rotational constant, BW=7/2 = 4011 MHz)

Nitrogen (I = 1) Hyperfine

Strongest transitions:DF = DJ5/2

June 21, 201166th International Symposium on Molecular Spectroscopy

FTMW Spectrometer

0 50 100 150 200 250 300

Time ( us)11409.4 11409.5 11409.6 11409.7 11409.8 11409.9 11410.0

Frequency ( MHz)

FFT

June 21, 201166th International Symposium on Molecular Spectroscopy

Synthesis• Fe + 0.25% (CN)2 in argon

• Nd/YAG laser• 532 nm (2nd harmonic)

• DC discharge• 1000 V

June 21, 201166th International Symposium on Molecular Spectroscopy

June 21, 201166th International Symposium on Molecular Spectroscopy

Results

June 21, 201166th International Symposium on Molecular Spectroscopy

Interpretation of h

Parameter FeCN CaNC

bF /MHz 12.48149(93)

c /MHz 2.0735(14)

h /MHz 2.55(19)

/m-3 2.23 × 1029 8.47 × 1029

FeCN (X4Di): [core] 8s29s23p410s211s21d34p2

bF ~ 0 (no s orbital contribution)

c : 3cos2q-1 = 2/7 (3dp), -4/7 (3dd)

small contributions from b and c

Scurlock et al. 1994

For FeCN:

For CaNC:

June 21, 201166th International Symposium on Molecular Spectroscopy

Conclusions

• FeCN has X4Di ground electronic state– Same as FeH, but different than FeF and FeCl (6Di), i.e. FeCN

more covalent than ionic

• Nitrogen hyperfine parameter, h, determined• Other early (Sc, Ti) and intermediate (V, Mn) metal cyanide

species need to be studied experimentally.• FeCN detectable in space (see talk TF06 later today)

June 21, 201166th International Symposium on Molecular Spectroscopy

Acknowledgements

• Prof. Lucy M. Ziurys• Dr. Michael A. Flory• Ziurys Group

• NSF• NASA