62nd OSU International Symposium on Molecular Spectroscopy TA12

Laser Spectroscopy of Iridium Monoboride

Jianjun Ye, H. F. Pang, A. M-Y. Wong, J. W-H. Leung,

and A. S-C. Cheung

Department of Chemistry, The University of Hong Kong,

Pokfulam Road, Hong Kong, P. R. China

1

Introduction

Some metal-containing boride molecules:

*The spectroscopic studies of diatomic metal-containing borides

are limited to the theoretical investigation.

*Experimental investigation of this series of molecules remains

almost unexplored. Only very few broide molecules:

PdB, studied by electron spin resonance (ESR) spectroscopy.

RhB, studied by laser induced fluorescence (LIF) spectroscopy.2

Present work

High resolution LIF spectrum of IrB between 545 to 610 nm

has been recorded and analyzed:

*(v, 0) with v = 0 – 3 of all four isotopic molecules: 191Ir10B, 193Ir10B, 191Ir11B and 193Ir11B were recorded.

*Partially resolved hyperfine structure conformed to case a

coupling scheme has been observed.

3

Experimental DetailsThe experimental setup of laser ablation/reaction and LIF

4

Molecule Production: Ir (Vapor) + B2H6 → IrB + etc.

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

Free Jet Expansion:

i) backing pressure: 5 atm (Ar + 1% B2H6)

ii) background pressure: 1x10-5Torr

Spectral line width: about 250MHz

5

Results and Analysis

Low-resolution LIF spectrum of ' = 2 – " = 3 band system of IrB

6

16500 17000 17500 18000 18500

191Ir10B

191Ir10B

193Ir11B

191Ir11B

(3,0)(2,0)(1,0)(0,0)

(3,0)(2,0)(1,0)

(0,0)

Wavenumber (cm-1)

The (0,0) band of the ' = 2 – " = 3 transition of IrB

7Wavenumber (cm-1)

16525 16530 16535 16540 16545 16550

P(J)

Q(J) R(J)

P(J)

Q(J)3

3

7 3

10 5 3753 193Ir10B

191Ir10B

193Ir11B10 5

14 10 575

3

191Ir11BR(J)

The (2,0) band of the ' = 2 – " = 3 transition of IrB

8

Wavenumber (cm-1)

17780 17785 17790 17795 17800

P(J)

P(J)Q(J)

Q(J)

R(J)

R(J)

3

3

3

3

3

191Ir11B

193Ir11B

7 5

10 5

85

7 5

10 5

105

Molecular constants for the ' = 2 and " = 3 states of IrB (cm-1)

9

Parameter 191Ir11B 193Ir11B 191Ir10B 193Ir10B

' = 2

T3 18350.286(2) 18349.943(2)

B 0.47235(3) 0.47204(3)

T2 17791.129(2) 17790.787(2)

B 0.47455(2) 0.47424(3)

T1 17186.970(2) 17186.679(2)

B 0.47321(2) 0.47294(2)

T0 16541.845(1) 16541.845(1) 16535.824(2) 16535.824(2)

B 0.47336(4) 0.47336(4) 0.51860(2) 0.51860(2)

" = 3

T0 0.000 0.000 0.000 0.000

B 0.51809(4) 0.51809(4) 0.56684 0.56684

Reduced term value plot of v = 2 level of = 2 and = 3 states of IrB

10

0 20 40 60 80 100 120 140 160

17784

17786

17788

17790

17792

17794

Tv-0

.45J(J

+1)

J(J+1)

Electronic configuration IrN 12 14 22 14

IrC 12 14 22 13

IrB 12 14 22 12 ?

2 1+ , 3¯ and 1

There is no = 3 substate from 2

Ir B

2p6s5d

3

2

1

1

2

1

Possible electronic configuration for the ground state of IrB

(1) 12 14 22 11 21 1, 3, 1, 3 (2) 12 14 22 22 1 , 3

Tentative assignmentGround state X 13 Excited state [ 16.5 ] 1 2

12

The (1,0) band of the ' = 2 – " = 3 transition of IrB with partially resolved hyperfine structure

Wavenumber (cm-1)

17185.0 17185.5 17186.0 17186.5

0.0401cm-1

0.0373cm-10.0506cm-1

0.0465cm-1

0.0620cm-1

Q'(5)

Q'(4)

Q'(3)

Q(5)

Q(4)

Q(3)

Q - 191Ir11BQ' - 193Ir11B

0.0584cm-1

Analysis of hyperfine structureHyperfine structure in the

[16.5] 12 - X 13 transition

Judging from the size of the atomic magnetic moment for both

Atom I (mag. dip.)193Ir 3/2 0.16

B 3/2 2.688

We ascribe the large hyperfine interaction to the B atom

zzzzhfs SIcSIbLIaΗ ˆˆˆˆˆˆˆ

In case a coupling scheme

)1(2

)]1()1()1([

JJ

JJIIFFhIFJΗIFJ hfs

)( cbah

For a 13 state ( = 3 and = 0)

h" = 3aFor a 12 state ( = 2 and = 0)

h' = 2a

Hyperfine structure

Q(3) line

Case a F = I + J

7/2

F

J = 3

12

J = 3

X13

9/2

5/23/2

9/2

7/2

5/2

3/2

q(F”)

15

The (1,0) band of the ' = 2 – " = 3 transition of IrB with partially resolved hyperfine structure

Wavenumber (cm-1)

17185.0 17185.5 17186.0 17186.5

0.0401cm-1

0.0373cm-10.0506cm-1

0.0465cm-1

0.0620cm-1

Q'(5)

Q'(4)

Q'(3)

Q(5)

Q(4)

Q(3)

Q - 191Ir11BQ' - 193Ir11B

0.0584cm-1

Using linewidth measured from the Q and P branches.

The hyperfine constants are estimated to be

X13 state h = 0.0286 cm-1

[16.5] 12 state h = 0.0116 cm-1

ah

3

"" hha

1cm00950 " - .a for X 13 state 1cm005800 ' - .a for [16.5] 12 state

iiNBN rgg

hca 3

4

1cm 00531.0

9293.02/3

6885.2 00318625.0

Summary

18

*Preliminary analysis of the rotational lines showed that

these vibronic bands are with ' = 2 and " = 3.

*Partially resolved hyperfine structure conformed to case

a coupling scheme has been observed.

Acknowledgments

19

This work was supported by grants from the

Research Grants Council of the Hong Kong SAR,

China (Project No. HKU 7015/04P) and Committee

on Research and Conference Grants, The University

of Hong Kong.