1. HIGH RESOLUTION LASER SPECTROSCOPY OF NICKEL MONOBORIDE, NiB
E. Scott Goudreau, Colan Linton, Dennis W. Tokaryk
Department of Physics and Centre for Laser, Atomic and Molecular
Sciences, University of New Brunswick, Fredericton, NB, Canada
Allan G. Adam
Department of Chemistry and Centre for Laser, Atomic and Molecular
Funding by NSERC

2. Previous work on NiB Theory:
D.Tzeli and A. Mavridis(J. Chem. Phys. 128 (2008) )
Extensive calculation of molecular properties
Predicted 2Σ+ ground state from π4σδ4 configuration
Experiment:
W. J. Balfour et al. (Chem. Phys. Lett. 463 (2008) 25-28)
Pulsed laser medium resolution spectra of 2 electronic transitions
Assigned as [19.7]2Σ+-X2Σ+ and [22.05]2Π- X2Σ+.
J. Zhen et al. (Chin. J. Chem. Phys. 23 (2010) )
Pulsed laser medium resolution spectra of a single electronic transition
Assigned as [20.77]2Π3/2- X2Σ+.
Need high resolution spectra to (a) examine fine and possibly hyperfine structure
(b)resolve discrepancy in results of 2 above experiments

3. UNB Experiments Laser ablation source: Ni + B2H6
Pulsed Laser: Medium resolution (FWHM~0.3 cm-1) survey scans
CW ring dye laser: High resolution (FWHM~0.006 cm-1) scans of strong bands

4. Low resolution (pulsed laser) spectrum
Only Zhen et al. bands observed with significant intensity

5. 2 – 0 Band (464nm)
Band Heads
58Ni11B
60Ni11B

6. Assignments Picked out 4 main branches (2 R and 2 P)
Rotational assignments of 2-0, 0-0, 3-0 bands of both isotopologues
Fits very well as 2Σ+ - 2Σ+ transition
Ground state: Regular 2Σ+ state . No distortion constants
Small spin rotation constant γ = cm-1
Excited state required D and H distortion terms for rotational and fine structure,
Very large spin-rotation γ = cm-1

7. Identity of Upper State?
Assigned as 2Σ+ with unusually large γ
Kopp and Hougen (Can. J. Phys. 45 (1967) )
2Σ state will fit equally well as a 2Π1/2 state
2Σ: Fine structure defined by spin-rotation constant γ
splitting e and f levels of equal N
2Π1/2: Fine structure defined by Λ-doubling constant p
splitting e and f levels of equal J
p = γ – 2B

8. Upper State v=2 Energies2Σ 2Π f e e f

9. Reduced term energy plots for upper state v=2
T – BN(N+1)
T – B(J+1/2)2 2Σ
2Π1/2
γ – p = cm-1
2B = cm-1
γ = cm-1
p = cm-1
Label upper state as case (c) Ω = 0.5 state [20.6]0.5
Fine structure described by p parameter

10. R11 band-head region of 58Ni11B 2 – 0 band9 1 N″
obs
calc
Partially resolved
Hyperfine structure
(11B I=3/2)

11. Magnetic Hyperfine Energies
e-levels N=J-1/2
Case (b)
2Σ State
f-levels N=J+1/2
C(J,F) = 0.5[F(F+1) – J(J+1) – I(I+1)]
Case (a)
2Π state
h = aΛ + (bF + 2c/3)Σ

12. Frosch and Foley Hyperfine Parameters
a/Hz
δi(r) = ψ2(0)
Use to estimate boron atomic orbital in ground state configuration

13. Ground State Configuration
X2Σ+ from π4σδ4 configuration
Unpaired σ orbital primarily Ni(3dσ) + small contribution from B(2sσ? 2pσ?)?
Observation of B hyperfine structure shows significant amount of B orbital
Use atomic parameters to calculate molecular hyperfine parameters bF and c
Morton and Preston (J. Magn. Reson. 30 (1978)
For Boron, <r-3> = a.u ψ2(0) = a.u.-3
<3cos2θ – 1> = 0 for sσ and +4/5 for pσ

14. Hyperfine constants (cm-1) of the [20. 6]0
Hyperfine constants (cm-1) of the [20.6]0.5 v = 2 and X2Σ+ v = 0 states of 58Ni11B h bF c
[20.6]0.5
(17)
X2Σ+ (obs)
0.0067(8)
0.0063(17)
X2Σ (calc sσ)
0.084
X2Σ (calc pσ)
0.0063
11B orbital contribution primarily 2pσ from ground B 2p 2P1/2 state!

15. Conclusions Zhen et al. transition reassigned as [20.6]0.5 – X2Σ+
Upper state is an Ω=0.5 state whose fine structure (ef parity splitting) is
represented by the p (Ω-doubling) parameter
Upper state requires 2nd and 3rd order distortion terms suggesting perturbation
Observation and preliminary analysis of partially resolved 11B hyperfine structure
shows that the σ orbital in the ground state has a small but significant contribution
from B(2pσ)
Need higher resolution experiments for a more complete analysis of hyperfine
structure