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: 191 Ir 10 B, 193 Ir 10 B, 191 Ir 11 B and 193 Ir 11 B were recorded. *Partially resolved hyperfine structure conformed to case a coupling scheme has been observed. 3
Experimental Details The experimental setup of laser ablation/reaction and LIF 4
Molecule Production : Ir (Vapor) + B 2 H 6 → IrB + etc. Vaporization Laser : Nd:YAG, 10Hz, 532nm, 5mJ Free Jet Expansion : i) backing pressure: 5 atm (Ar + 1% B 2 H 6 ) ii) background pressure: 1x10 -5 Torr Spectral line width : about 250MHz 5
Results and Analysis Low-resolution LIF spectrum of ' = 2 – " = 3 band system of IrB 6 Wavenumber (cm -1 )
The (0,0) band of the ' = 2 – " = 3 transition of IrB 7 Wavenumber (cm -1 )
The (2,0) band of the ' = 2 – " = 3 transition of IrB 8 Wavenumber (cm -1 )
Molecular constants for the ' = 2 and " = 3 states of IrB (cm -1 ) 9 Parameter 191 Ir 11 B 193 Ir 11 B 191 Ir 10 B 193 Ir 10 B ' = 2 T3T (2) (2) B (3) (3) T2T (2) (2) B (2) (3) T1T (2) (2) B (2) (2) T0T (1) (2) B (4) (2) " = 3 T0T B (4)
Reduced term value plot of v = 2 level of = 2 and = 3 states of IrB 10
Electronic configuration IrN 1 2 1 4 2 2 1 4 IrC 1 2 1 4 2 2 1 3 IrB 1 2 1 4 2 2 1 2 ? 2 1 +, 3 ¯ and 1 There is no = 3 substate from 2 IrB 2p 6s 5d 33 22 11 11 22 11 Possible electronic configuration for the ground state of IrB (1) 1 2 1 4 2 2 1 1 2 1 1 , 3 , 1 , 3 (2) 1 2 1 4 2 2 2 21 , 3 Tentative assignment Ground state X 1 3 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 )
Analysis of hyperfine structure Hyperfine structure in the [16.5] 1 2 - X 1 3 transition Judging from the size of the atomic magnetic moment for both AtomI (mag. dip.) 193 Ir3/20.16 B3/ We ascribe the large hyperfine interaction to the B atom In case a coupling scheme
For a 1 3 state ( = 3 and = 0) h" = 3a For a 1 2 state ( = 2 and = 0) h' = 2a Hyperfine structure Q(3) line Case a F = I + J 7/2 F J = 3 1212 X13X13 9/2 5/2 3/2 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 )
Using linewidth measured from the Q and P branches. The hyperfine constants are estimated to be X 1 3 state h = cm -1 [16.5] 1 2 stateh = cm -1
for X 1 3 state for [16.5] 1 2 state
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.