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

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.

OUTLINE 3 Introduction Experimental section Results and discussion Summary

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

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

Schematic diagram for experimental setup 6

We observed 33 bands between – 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

Broadband scan of IrP 8

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

Molecular constants for [21.7] 0 + state 10 v' – v"TvBv 4 – † † 3 – † † 2 – † † 1 – – † Values from Adam et. al. ( B = cm -1 for the X 1 Σ + ) 193 IrP 191 IrP

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

We observed 33 bands between – 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

Broadband scan of IrP 13

Molecular constants for [23.7] 0 + state 14 v' – v"TvBv 2 – – –

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

Reduced term value plot [23.6] 16 Tv = cm -1 Bv = cm -1

Molecular constants for [23.6] 0 + state 17 v' – v" TvTv BvBv 3 – – – –

We observed 33 bands between – 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

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

Series 2 transition band: 20

Molecular Constants for Series 1 and 2 of 193 IrP Series 1Series 2 v' – v"TvBvTvBv V? V=4?

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

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 : cm-1

Molecular constants for [21.2] 0 + – X 1 Σ + transition 24 v' – v"TvBv 2 – – –

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 : cm -1

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

Conclusions 27 (1)Ground state bond length : 1.993Å ΔG 1/2 : 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

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