Probing the electronic structure of the Nickel Monohalides: Spectroscopy of the low-lying electronic states of NiX (X=Cl , Br , I).

Lloyd MuzangwaMolecular Spectroscopy and Dynamics Group

M+

X-

66th 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 2D5/2

Ground state NiBr, NiCl and NiF identified to be 2P3/2

NiBr, the next highest state A2D5/2 from ground state is only 37.25 cm-1 above the X2P3/2.

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 3d9 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: YAGLaser

Dye laser

HV R2 R1

PC

PC

Spectrograph

PMT

Digital D

elay G

eneratorDigital Oscilloscope

Cath

ode

Lam

p

Lab picture

Proposed Mechanism

LASER

High pressure Ar

precursor: halogen containing:

VACUUM

DISCHARGE

DETECTORPMT/Spectrograph

CH3I, CD3I

CH2Br2 C2Cl4

Low Resolution LIF for NiI

SVL spectra of NiI recorded via:

[21.1]2P3/2 v=0

[21.3]2D5/2 v=0

* Discharge background

SVL spectra of NiI via [21.6]2P3/2 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

T0

Term Energy

0 162.7 (1)

164

139

787.8 (2)

…………

812

1529.8 (1)

……………

1332

2140.2 (2)

……………

2210

This work

Ref. [30]

Ref. [35]

we

Vibrational

Frequency

278.5 (0.3)

276b

276.67b

290

273.2 (0.7)

271b

…………..

283

260.0 (5)

………….

…………..

274

277.5 (1)

…………

…………..

287

268.0 (2)

…………..

………….

281

This work

Ref. [48]

Ref. [30]

Ref. [35]

Xe

-0.74 (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

X 2

5/ 2 A2

3/ 2 A2

1/ 2 X 2

3/ 2 B 2

1/ 2

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]2D5/2 v=1

Rs = 600 lines/mm

Rs = 1800 lines/mm

X2P3/2 A2D5/2 X2P1/2 A2D3/2 B2S+1/2

Source

T0

0 43.3(1)

37b

165

488.9(1)

……………

583

1537.7(1)

…………….

1453

1843.1(1)

……………..

2214

This work

Ref [31]

Ref [35]

we

320.4(0.5)

331

336

326.9(1)

317

345

307.0(0.8)

…………

328

326.9(1)

……………

344

324.6(1)

…………..

335

This work

Ref [31]

Ref [35]

xe

-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).

X2P3/2 A2D5/2 X2P1/2 A2D3/2 B2S+1/2

Source

T0

0 166.9(1.7)a

268

158b

388.5 (0.2)

473

386

1654.3(2.5)

1549

1646

1776.5(10.2)

2002

1768

This work

Ref.[35]

Ref.[23, 24]

we

427.4 (1.7)

433

426

435.1 (1.6)

440

436

403.4 (0.9)

420

---------------

433.1 (2.1)

439

432

425.56 (7.9)

433

------------------

This work

Ref.[35]

Ref.[23, 24]

xe

-1.81 (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

we

NiBr we NiCl

we NiF we

B2S+1/2

268 B2S+

1/2 324 B2S+1/2 425 A2D3/2 645

     

X2D 3/2 277 A2D3/2 326 A2D3/2 433 B2S+1/2 648

       

A2P 1/2 260 X2P1/2 307 X2P1/2 404 A2D5/2 646

       

A2P3/2 273 A2D5/2 326 A2D5/2 435 X2P1/2 607

       

X2D5/2 278

X2P3/2 320 X2P3/2 427 X2P3/2 637

Periodic trends in nickel monohalidesExperimental work

Theoretical work

SA-C

ASSC

F Ba

sis

set:

DKH

2

Spin orbit splitting of 2D and 2P

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 21 000- 24 000 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 A2P3/2 and X2D3/2 states and A2P1/2 and B2S+

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. TheoryRed Solid Square - theoretical

Blue open square - Experimental

SVL spectrum for NiBr

SVL spectra of NiCI