laser spectroscopy of iridium monophosphide h. f. pang, y. xia, a. w. liu and a. s-c. cheung...
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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 + 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)
7
Broadband scan of IrP
8
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
11
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)
12
Broadband scan of IrP
13
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
14
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
17
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)
18
Spectra of Series 1 and Series 2
19
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
16
Series 2 transition band:
20
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:
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 ΔG1/2 : 569.6 cm-1
Molecular constants for [21.2] 0+ – X 1Σ+ transition
24
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
25
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
26
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
27
(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.)
28
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