1. Laser spectroscopy of Iridium monophosphide H. F. Pang, Y. Xia, A. W. Liu and A. S-C. Cheung Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. China 1 64th OSU International Symposium on Molecular Spectroscopy

2. ACKNOWLEDGMENTS 2 This work was supported by grants from the Research Grants Council of the Hong Kong SAR, China (Project No. HKU 7015/07P) and Committee on Research and Conference Grants, The University of Hong Kong. We would like to thank Prof. Allan Adam and Prof. Colan Linton for communicating to us their IrP molecular constants before publication and Prof. C. Western for the use of his PGOPHER program.

3. OUTLINE 3 Introduction Experimental section Results and discussion Summary

4. Why iridium-containing compounds?  Many Ir compounds are good catalysts for hydrogenation of alkenes and alkynes, reduction of nitrogenous function groups etc.  The spectroscopic studies of diatomic iridium-containing compounds are limited.  Try to understand the systematic trend across the main group compounds (IrB, IrC, IrN IrO and IrF). 4 INTRODUCTION

5. EXPERIMENTAL CONDITIONS Molecule production : laser ablation/reaction free jet expansion Ir + PH 3 (1% in Ar) → IrP + etc. Ablation Laser : Nd:YAG, 10Hz, 532nm, 5mJ Free Jet Expansion : i) backing pressure: 6 atm (1% PH 3 + Ar) ii) background pressure: 1x10 -5 Torr LIF spectrum between 385 and 520 nm Spectral linewidth: Pulsed dye laser ( ~0.05cm -1 ) 5

6. Schematic diagram for experimental setup 6

7. We observed 33 bands between 20100 – 25600 cm -1 for IrP: 1. [21.2] 0 + – X 1 Σ + transition (3 bands) 2. [21.7] 0 + – X 1 Σ + transition (Prof. Adam et al.) (5 bands) 3.[23.6] 0 + – X 1 Σ + transition (4 bands) 4.[23.7] 0 + – X 1 Σ + transition (3 bands) 5.Series 1 and 2 transitions (10 bands) 6.Unclassified bands (8 bands) 7

8. Broadband scan of IrP 8

9. The [21.7] 0 + – X 1 Σ + (0,0) band of IrP 9

10. Molecular constants for [21.7] 0 + state 10 v' – v"TvBv 4 – 0 23 499.00 23 498.903 † 0.1370 0.136 35 † 3 – 0 23 063.91 23 063.410 † 0.1376 0.138 21 † 2 – 0 22 626.35 22 625.727 † 0.1388 0.138 26 † 1 – 022 187.630.1392 0 – 021 746.270.1395 † Values from Adam et. al. ( B = 0.150939 cm -1 for the X 1 Σ + ) 193 IrP 191 IrP

11. Observed and simulated IrP spectrum 11 Conditions: Linewidth: Lorentzian comp. = 0.1 cm -1 Temperature: 45K

12. We observed 33 bands between 20100 – 25600 cm -1 for IrP: 1. [21.2] 0 + – X 1 Σ + transition (3 bands) 2. [21.7] 0 + – X 1 Σ + transition (Prof. Adam et al.) (5 bands) 3.[23.6] 0 + – X 1 Σ + transition (4 bands) 4.[23.7] 0 + – X 1 Σ + transition (3 bands) 5.Series 1 and 2 transitions (10 bands) 6.Unclassified bands (8 bands) 12

13. Broadband scan of IrP 13

14. Molecular constants for [23.7] 0 + state 14 v' – v"TvBv 2 – 024567.120.1374 1 – 024141.100.1384 0 – 023702.100.1392

15. The [23.6] 0 + – X 1 Σ + (0,0) band of IrP 15

16. Reduced term value plot [23.6] 16 Tv = 23 570.98 cm -1 Bv = 0.1372 cm -1

17. Molecular constants for [23.6] 0 + state 17 v' – v" TvTv BvBv 3 – 0 24840.910.1359 2 – 0 24424.770.1351 1 – 0 23997.520.1344 0 – 0 23570.980.1372

18. We observed 33 bands between 20100 – 25600 cm -1 for IrP: 1. [21.2] 0 + – X 1 Σ + transition (3 bands) 2. [21.7] 0 + – X 1 Σ + transition (Prof. Adam et al.) (5 bands) 3.[23.6] 0 + – X 1 Σ + transition (4 bands) 4.[23.7] 0 + – X 1 Σ + transition (3 bands) 5.Series 1 and 2 transitions (10 bands) 6.Unclassified bands (8 bands) 18

19. Spectra of Series 1 and Series 2 19 Series 1Series 2 193 IrP 191 IrP

20. Series 2 transition band: 20

21. Molecular Constants for Series 1 and 2 of 193 IrP Series 1Series 2 v' – v"TvBvTvBv 25 598.260.134825 028.320.1347 25 180.190.132824 610.410.1325 24 755.510.135824 185.900.1349 V?24 321.700.136323 752.230.1357 V=4?23 878.240.135423 308.440.1350 21

22. SERIES 1 AND 2 TRANSITIONS 22 ΔG 1/2 : 569.6 cm -1

23. Questions: 23 (1)The isotopic separations  high v level - no other electronic states in the vicinity is observed (2)Molecular constants are nearly the same  the upper states are in common - The separation is ΔG 1/2 : 569.6 cm-1

24. Molecular constants for [21.2] 0 + – X 1 Σ + transition 24 v' – v"TvBv 2 – 022 053.920.1356 1 – 021 618.330.1396 0 – 021 176.120.1398

25. MOLECULAR ORBITAL OF IRP 25 2π is a slightly antibonding orbital 1δ is a non-bonding orbital 2σ is a bonding orbital X 1 Σ + 1σ 2 2σ 2 1π 2 1δ 4 Ground state bond length : 1.993Å ΔG 1/2 : 569.6 cm -1

26. Electronic configurations of low-lying states of IrP 26 LabelMolecular Orbital OccupanciesConfigurationStates 11 11 22 11 22 33 44 A2424Close shell X1+X1+ B24141  1, 31, 3 C24141  1 , 3  D24231  3 , 3 , 1 , 1  E24231  1 , 3  F23241  1  , 3    1  , 3    1 , 3  G23241  1 , 3  H24141  1, 31, 3

27. Conclusions 27 (1)Ground state bond length : 1.993Å ΔG 1/2 : 569.6 cm-1 (2)All states observed are of 0 + symmetry (3)Upper state vibrational separations : 440 – 416 cm -1 (4) More work is needed: Life time measurements Resolved fluorescence spectrum

28. Isoelectronic molecules : all have X 1  + state RhN IrN PtC( 1 and 0 + states observed) RhP (only 0 + upper states obs.) 28