1. Fourier Transform Emission Spectroscopy of CoH and CoD
Iouli E. Gordon
Robert J. LeRoy
Peter F. Bernath
Departments of Physics and Chemistry

2. Previous work A 3Φ3 A 3Φ4 A. Heimer, Z. Phys. 104, 448(1937)
Measured (0,0) and (1,0) bands at and nm
A′ 3Φ3
A′ 3Φ4
Klynning et al., Phys. Scr. 6, 61(1972), 7, 72(1973), 24, 21(1981)
Recorded and rotationally analyzed:
CoD: A 3Φ4─ X 3Φ4: (0,0), (1,1), (1,0), (2,1), (0,1) and (1,2)
A 3Φ3─ X 3Φ3: (0,0), (1,0)
CoH: A 3Φ4─ X 3Φ4: (0,0), (1,1), (1,0)
A 3Φ3─ X 3Φ3: (0,0), (0,1)
Ω=±1 transitions were not observed in these works
~22000 cm-1
Ram et al., J. Mol. Spectrosc. 175, 1
Recorded Fourier transform emission spectra of (0,0) and (0,1) bands of A′ 3Φ4- X3Φ4 transition and (0,0) band of A′ 3Φ3- X3Φ3 transition for CoH.
Varberg et al., J. Mol. Spectrosc. 138, 630 (1989)
Recorded several bands by laser excitation spectroscopy and observed resolved fluorescence from an excited Ω=3 spin component, which enabled to find a new electronic state ~2470 cm-1 above X3Φ4 as well as to determine spin-orbit splitting between Ω”=4 and 3 components (728(±3) cm-1)
Barnes et al., J. Mol. Spectrosc. 173, 100
Recorded sub-Doppler spectra of CoH and CoD A’ 3Φ4- X3Φ4 transition using laser excitation spectroscopy. Studied hypefine structure in (0,0) band and lower resolution spectra of transitions from (5,0) to (0,0) for both molecules. Extended Varberg’s resolved fluorescence results to CoD.
~12400 cm-1
33
X3Φ3
X3Φ4

3. Previous work
Freindorf et al.,
J. Chem. Phys. 99, 1215 (1993)

4. Motivation for this work
So far only transitions involving Ω=4 and Ω=3 components of the ground state have been observed (Ω=2 is missing)
Ω=±1 transitions were not observed at high resolution in previous works
Only one parity component was assigned in the X 3Φ3 state
There is not sufficient data for Dunham and combined isotopologue fits of CoH and CoD
Search for the new electronic transitions

5. King Furnace

6. Experimental details Region: 15500-8500 cm-1 Beamsplitter: Quartz
Lens and windows: BaF2
Optical filter: nm red pass
Detector: Si:diode
Resolution: cm-1
Number of scans: ~200
Region: cm-1
Beamsplitter: CaF2
Lens and windows: BaF2
Optical filter: cm-1 blue pass
Detector: InSb
Resolution: cm-1
Number of scans: ~200

7. Part of the CoD spectrum A′ 3Φ-X 3Φ
V=-1
V=0
V=+1
V=-2
V=+2

8. CoH infrared electronic transition

9. Assigned transitions We have assigned and analyzed:
CoD: A′ 3Φ4─ X 3Φ4: (0,0), (2,0), (1,0), (2,1), (0,1), (1,2), (2,3), (0,2) and (1,3)
A’ 3Φ3─ X 3Φ3: (0,0)
CoH: A′ 3Φ4─ X 3Φ4: (0,0), (2,0), (1,0), (0,1), (1,2)
A′ 3Φ3─ X 3Φ3 : (0,0)
A′ 3Φ3─ X 3Φ4: (0,0)
A′ 3Φ4─ X 3Φ3: (0,0)
One of the parity components of the X 3Φ3 state is perturbed in CoH. The only close-lying (according to ab initio calculations) electronic state that can cause this is a 3Σ- state, which has a 0+ component of e parity. This observation suggests a parity assignment of the lines and places a 0+ component of 3Σ- state at ~700 cm-1.

10. Band-by-band fit
The excited electronic state was fit to the term values, when ground state rotational levels were fit to the following case (c) expression:
After that the ground state constants were held fixed to the well determined values from the previous fit and Watson's "Robust" data weighting procedure was employed [J. Mol. Spectrosc. 219, 326 (2003)] in order to obtain reasonable excited state spectroscopic constants.

11. Numbers in parenthesis are 2σ in units of the last digit
X 3Φ4
v=0
v=1
v=2 Tv
(70)
(95) Bv
(170)
(200)
(38)
104 x Dv
(100)
(110)
3.942 (41)
108x Hv
0.845 (22)
3.33 (22)
5.8 (99)
1011x Lv
(170)
(150)
(25)
1011x qL
(110)
2.354 (100)
1.60 (65)
1015x qM
-8.60 (80)
(70)
-300 (40)
A′ 3Φ4
v=0
v=1
v=2 Tv
(85)
(130)
(150) Bv
(69)
(190)
(40)
104 x Dv
(140)
-3.68 (66)
-8.43 (33)
106x Hv
1.760 (73)
9.33 (75)
6.04 (85)
1011x Lv -
-6.20 (24)
108x qL
1.003 (39)
0.532 (55)
0.472 (99)
1011x qM
-8.30 (35)
-3.10 (28)
-2.01 (53)
Numbers in parenthesis are 2σ in units of the last digit

12. Ground and excited state constants for Ω=3 components (in cm-1)
X 3Φ3 (v=0)
A′ 3Φ3 (v=0) Tv
(23)
(23) Bv
(31)
(110)
103 x Dv
(110)
(96)
106x Hv
(20)
1.130 (33)
1010x Lv -
-6.00 (39)
106x qH
(38)
(72)
109x qL
2.476 (26)

13. Combined-isotopologue fit
Apart from Dunham fits of both molecules a combined- isotopologue fit was carried out using the following model:
CoD was chosen as the reference isotopologue, since there is more vibrational data for that molecule than for CoH

14. Combined-isotopologue fit
Gv parameters:
YLM( 1,0)= (120)
YLM( 2,0)= (69)
YLM( 3,0)= e-02 (110)
Bv parameters:
YLM( 0,1)= (74)
YLM( 1,1)= e-02 (59)
YLM( 2,1)= 0.93e-04 (16)
-Dv parameters:
YLM( 0,2)= e-04 (240)
YLM( 1,2)= e-06 (160)
YLM( 2,2)= 1.45e-07 (37)
Hv parameters:
YLM( 0,3)= e-09 (270)
YLM( 1,3)= e-09 (150)
Lv parameters:
YLM( 0,4)= e-13 (110)
YLM( 1,4)= 1.10e-13 (63)
Lambda-doubling Dunham-type
expansion coefficients:
qLM( 0,4) = 3.84e-14 (80)
qLM( 1,4) = e-13 (120)
qLM( 2,4) = 8.04e-14 (32)
qLM( 0,5) = 0.17e-17 (37)
qLM( 1,5) = -1.50e-17 (26)
Born-Oppenheimer breakdown
parameters:
δ( D; 1,0)= e-01 (110)
δ( D; 2,0)= -0.33e-02 (27)
δ( D; 0,1)= e-02 (81)
δ( D; 1,1)= e-03 (68)
δ( D; 2,1)= e-04 (160)
δ( D; 0,2)= e-06 (140)
δ( D; 1,2)= 4.30e-07 (51)
δ( D; 0,3)= e-09 (74)

15. Conclusions and Future Work
Electronic spectra of CoH and CoD in the red and infrared were investigated using a Fourier transform spectrometer. The recorded bands considerably extend available vibrational and rotational information for the ground electronic state.
Ω=±1 transitions were observed for CoH allowing accurate determination of the spin-orbit splitting between Ω=4 and 3 components.
Band-by-band, Dunham and combined-isotopologue fits were carried out.
New electronic transitions were observed, but were not identified yet.
Financial support from NSERC is gratefully acknowledged.