Probing the electronic structure of the Nickel Monohalides: Spectroscopy of the low-lying electronic states of NiX (X=Cl, Br, I). Lloyd Muzangwa Molecular Spectroscopy and Dynamics Group M+M+ X-X- 66 th International symposium on molecular spectroscopy

 Our current understanding of nickel monohalides owes much to seminal studies of NiH by field and co-workers, the hydride served as a model for the spectroscopy of the heavier halides.  Leung and co-workers using laser vaporization/free jet expansion and LIF identified : Ground state NiH and NiI identified to be 2  5/2 Ground state NiBr, NiCl and NiF identified to be 2  3/2  NiBr, the next highest state A 2  5/2 from ground state is only cm -1 above the X 2  3/2.  The close proximity of the low-lying states in these species results in many perturbations. What is known of Nickel monohalides ? Cheung, et al, Journal of Chemical Physics, 119(23) (2003). J.W.H. Leung, et al, Journal of Chemical Physics, 117 (2002).

Why study SVL emission of nickel monohalides?  Gives complete vibrational data for the five low- lying electronic states associated with 3d 9 configuration of Ni +  Reveals the presence of perturbation among the low-lying states  Complete analysis of NiCI, NiI and NiBr constants allow a detailed study of periodic trends within the nickel monohalide series.

Nd: YAG Laser Dye laser HVR2R2 R1R1 PC Spectrograph PMT Digital Delay Generator Digital Oscilloscope Cathode Lamp

Lab picture

Proposed Mechanism LASER High pressure Ar precursor: halogen containing: VACUUM DISCHARGE DETECTOR PMT/Spectrograph CH 3 I, CD 3 I CH 2 Br 2 C 2 Cl 4

Low Resolution LIF for NiI

SVL spectra of NiI recorded via : [21.1] 2  3/2 v=0 [21.3] 2  5/2 v=0 * Discharge background

SVL spectra of NiI via [21.6] 2  3/2 v=2 * Discharge background Comparison of SVL spectra recorded via different vibrational levels in the excited states show an intensity pattern reflecting the nodal structure of the vibrational wavefunction.

Source T 0 Term Energy (1) (2) ………… (1) …………… (2) …………… 2210 This work Ref. [30]30 Ref. [35]35  e Vibrational Frequency (0.3) 276 b b (0.7) 271 b ………… (5) …………. ………… (1) ………… ………… (2) ………….. …………. 281 This work Ref. [48]48 Ref. [30]30 Ref. [35]35 XeXe (0.03)-0.85 (0.06)-0.45 (1.25)-0.89 (0.17)0.02 (0.36)This work Experimental constants (in cm -1 ) for NiI One standard error given in parenthesis; b anharmonic values. [30] W.S. Tam, et al, Journal of Chemical Physics, 119 (2003) [35] W.L. Zou, W.J. Liu, Journal of Chemical Physics, 124 (2006). [48] W.S. Tam, et al, Journal of Chemical Physics, 121 (2004)

Low resolution LIF spectra of NiBr

PGOPHER Simulations for NiBr

SVL spectrum for NiBr via [21.8] 2  5/2 v=1 Rs = 600 lines/mm Rs = 1800 lines/mm

X 2  3/2 A 2  5/2 X 2  1/2 A 2  3/2 B 2  + 1/2 Source T0T (1) 37 b (1) …………… (1) …………… (1) …………… This work Ref [31]31 Ref [35]35 ee 320.4(0.5) (1) (0.8) ………… (1) …………… (1) ………… This work Ref [31]31 Ref [35]35 xexe -0.77(0.09)-0.81(0.18)-0.95(0.10)-0.93(0.13)-1.26(0.13)This work Experimental vibrational constants for NiBr One standard error given in parenthesis; b anharmonic values. [31] E. Yamazaki, et al, Journal of Chemical Physics, 121 (2004). [ 35] W.L. Zou and W.J. Liu, Journal of Chemical Physics, 124 (2006).

X 2  3/2 A 2  5/2 X 2  1/2 A 2  3/2 B 2  + 1/2 Source T0T (1.7) a b (0.2) (2.5) (10.2) This work Ref.[35]35 Ref.[23, 24]2324 ee (1.7) (1.6) (0.9) (2.1) (7.9) This work Ref.[35]35 Ref.[23, 24]2324 xexe (0.49)-1.62 (0.26)-0.35(0.15)-1.94 (0.28)-1.70 (1.11)This work Experimental vibrational constants NiCI a One standard error given in parenthesis; b anharmonic values. [23] A. Poclet, et al, J Mol Spectroscopy, 204 (2000) [24] Y. Krouti, et al, J Mol Spectroscopy, 210 (2001) [35] W.L. Zou, and W.J. Liu, Journal of Chemical Physics, 124 (2006)

Perturbations in NiI and NiBr NiI NiBr

Periodic trends Vibrational constants in cm -1. NiI ee NiBr ee NiCl ee NiF ee B 2  + 1/2 268 B 2  + 1/2 324 B 2  + 1/2 425 A 2  3/2 645 X 2  3/2 277 A 2  3/2 326 A 2  3/2 433 B 2  + 1/2 648 A 2  1/2 260 X 2  1/2 307 X 2  1/2 404 A 2  5/2 646 A 2  3/2 273 A 2  5/2 326 A 2  5/2 435 X 2  1/2 607 X 2  5/2 278 X 2  3/2 320X 2  3/2 427 X 2  3/2 637

Periodic trends in nickel monohalides Experimental work Theoretical work SA-CASSCF Basis set: DKH2

Spin orbit splitting of 2  and 2 

 Laser induced fluorescence and single vibronic level emission spectroscopy has been used to probe five low-lying electronic states of NiI, NiBr and NiCI in the range cm -1.  The excited band structure was composed of isotope splitting.  Homogeneous (spin –orbit) perturbations have been identified and results from interactions between vibrational levels of the A 2  3/2 and X 2  3/2 states and A 2  1/2 and B 2  + 1/2 states.  In contrast to NiI, the spectra of NiBr and NiCl show few vibronic perturbations, reflecting the smaller spin-orbit coupling in these systems.  Overall, the computed spectroscopic constants and simulations were in good agreement with available theoretical data. Conclusion

 It would be interesting to compare trends for series with other transition metals.  Looking into polyatomic series example NiOH. Forward Thinking

Acknowledgements Isaac Newton, “ If l have been able to see further than others, it is because l have stood on the shoulders of giants ” Thanks to Dr Scott Reid, My lab mates, and All for listening!!!!!!!!!!!!!!!!!!!!!!!

Supporting slides

Experiment vs. Theory Red Solid Square - theoretical Blue open square - Experimental

SVL spectrum for NiBr

SVL spectra of NiCI