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 ee 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 ee (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 ee NiBr ee NiCl ee NiF ee 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