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

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• 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).

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INTRODUCTION

EXPERIMENTAL CONDITIONS

Molecule production : laser ablation/reaction free jet expansion

Ir + PH3 (1% in Ar) → IrP + etc.

Ablation Laser : Nd:YAG, 10Hz, 532nm, 5mJ

Free Jet Expansion : i) backing pressure: 6 atm (1% PH3+ Ar)

ii) background pressure: 1x10-5Torr

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 20100 – 25600 cm-1 for IrP:

1. [21.2] 0+ – X 1Σ+ transition (3 bands)

2. [21.7] 0+ – X 1Σ+ transition (Prof. Adam et al.) (5 bands)

3. [23.6] 0+ – X 1Σ+ transition (4 bands)

4. [23.7] 0+ – X 1Σ+ transition (3 bands)

5. Series 1 and 2 transitions (10 bands)

6. Unclassified bands (8 bands)

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Broadband scan of IrP

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22600 22700 22800 22900 23000 23100 23200 23300 23400 23500 23600

(2,0) (4,0)

Wavenumber (cm-1)

[21.7] 0+ X1+

(3,0)

Adam et. al.

21730 21735 21740 21745 21750

14

3

20 15 10 5

Wavenumber (cm-1)

P

R

1

0

193IrP and 191IrP

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

9

Molecular constants for [21.7] 0+ state

10

v' – v" Tv Bv

4 – 0 23 499.0023 498.903†

0.13700.136 35†

3 – 0 23 063.9123 063.410†

0.1376 0.138 21†

2 – 0 22 626.3522 625.727†

0.13880.138 26†

1 – 0 22 187.63 0.1392

0 – 0 21 746.27 0.1395

† Values from Adam et. al. ( B = 0.150939 cm-1 for the X 1Σ+ )

193IrP191IrP

Observed and simulated IrP spectrum

21730 21735 21740 21745 21750

Wavenumber (cm-1)

Experiment Simulation

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Conditions:

Linewidth: Lorentzian comp. = 0.1 cm-1

Temperature: 45K

We observed 33 bands between 20100 – 25600 cm-1 for IrP:

1. [21.2] 0+ – X 1Σ+ transition (3 bands)

2. [21.7] 0+ – X 1Σ+ transition (Prof. Adam et al.) (5 bands)

3. [23.6] 0+ – X 1Σ+ transition (4 bands)

4. [23.7] 0+ – X 1Σ+ transition (3 bands)

5. Series 1 and 2 transitions (10 bands)

6. Unclassified bands (8 bands)

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Broadband scan of IrP

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23600 23700 23800 23900 24000 24100 24200 24300 24400 24500 24600 24700

(2,0)(1,0)

Series 2

Series 1

Wavenumber (cm-1)

[23.7] 0 -- X 1+

(0,0)

Molecular constants for [23.7] 0+ state

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v' – v" Tv Bv

2 – 0 24567.12 0.1374

1 – 0 24141.10 0.1384

0 – 0 23702.10 0.1392

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

1523560 23565 23570

913

50

15 10 5

Wavenumber (cm-1)

1

perturbation

Reduced term value plot [23.6]

160 50 100 150 200 250 300 350

23571.0

23571.5

23572.0

23572.5

23573.0

J(J+1)

Tv

- 0

.13

3J(

J+1

)

Tv = 23 570.98 cm-1

Bv = 0.1372 cm-1

Molecular constants for [23.6] 0+ state

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v' – v" Tv Bv

3 – 0 24840.91 0.1359

2 – 0 24424.77 0.1351

1 – 0 23997.52 0.1344

0 – 0 23570.98 0.1372

We observed 33 bands between 20100 – 25600 cm-1 for IrP:

1. [21.2] 0+ – X 1Σ+ transition (3 bands)

2. [21.7] 0+ – X 1Σ+ transition (Prof. Adam et al.) (5 bands)

3. [23.6] 0+ – X 1Σ+ transition (4 bands)

4. [23.7] 0+ – X 1Σ+ transition (3 bands)

5. Series 1 and 2 transitions (10 bands)

6. Unclassified bands (8 bands)

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Spectra of Series 1 and Series 2

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Series 1 Series 2

193IrP 193IrP 191IrP191IrP

23300 23305 23310

5

5

13 10 5

014 10 5 1

0R

R

P

191IrP193IrP

191IrP

Wavenumber (cm-1)

193IrP

P

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Series 2 transition band:

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Molecular Constants for Series 1 and 2 of 193IrP

Series 1 Series 2

v' – v" Tv Bv Tv Bv

25 598.26 0.1348 25 028.32 0.1347

25 180.19 0.1328 24 610.41 0.1325

24 755.51 0.1358 24 185.90 0.1349

V? 24 321.70 0.1363 23 752.23 0.1357

V=4? 23 878.24 0.1354 23 308.44 0.135021

-1000

-500

0

500

1000

24000

27000

2502

8

2461

1

2418

5

2375

2

2330

8

2559

8

2518

0

2475

5

2432

1

v=1

Ter

m V

alu

e

v=0569.6cm-1

443.80433.10

425.25417.18

2387

8

0+ state

' state

IrPSERIES 1 AND 2 TRANSITIONS

22ΔG1/2 : 569.6 cm-1

Questions:

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(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 ΔG1/2 : 569.6 cm-1

Molecular constants for [21.2] 0+ – X 1Σ+ transition

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v' – v" Tv Bv

2 – 0 22 053.92 0.1356

1 – 0 21 618.33 0.1396

0 – 0 21 176.12 0.1398

MOLECULAR ORBITAL OF IRP

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2π is a slightly antibonding orbital

1δ is a non-bonding orbital

2σ is a bonding orbital

X 1Σ+ 1σ2 2σ2 1π2 1δ4

Ground statebond length : 1.993ÅΔG1/2 : 569.6 cm-1

Electronic configurations of low-lying states of IrP

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Label Molecular Orbital Occupancies Configuration States

1 1 2 1 2 3 4

A 2 4 2 4 Close shell X1+

B 2 4 1 4 1 1, 3

C 2 4 1 4 1 1, 3

D 2 4 2 3 1 3, 3, 1, 1

E 2 4 2 3 1 1, 3

F 2 3 2 4 1 1, 31, 31, 3

G 2 3 2 4 1 1, 3

H 2 4 1 4 1 1, 3

Conclusions

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(1) Ground state bond length : 1.993Å

ΔG1/2 : 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

Isoelectronic molecules : all have X 1+ state

RhN IrN PtC ( 1 and 0+ states observed)

RhP (only 0+ upper states obs.)

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