62 nd OSU International Symposium on Molecular Spectroscopy

62 nd OSU International Symposium on Molecular Spectroscopy TA 12 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 theoretical investigation. *Experimental investigation of this series of molecules remains almost unexplored. Only very few broide molecules: Pd. B, studied by electron spin resonance (ESR) spectroscopy. Rh. B, studied by laser induced fluorescence (LIF) spectroscopy. 2

Present work High resolution LIF spectrum of Ir. B between 545 to 610 nm has been recorded 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 → Ir. B + etc. Vaporization Laser: Nd: YAG, 10 Hz, 532 nm, 5 m. J Free Jet Expansion: i) backing pressure: 5 atm (Ar + 1% B 2 H 6) ii) background pressure: 1 x 10 -5 Torr Spectral line width: about 250 MHz 5

Results and Analysis Low-resolution LIF spectrum of ' = 2 – " = 3 band system of Ir. B Wavenumber (cm-1) 6

The (0, 0) band of the ' = 2 – " = 3 transition of Ir. B Wavenumber (cm-1) 7

The (2, 0) band of the ' = 2 – " = 3 transition of Ir. B Wavenumber (cm-1) 8

Molecular constants for the ' = 2 and " = 3 states of Ir. B (cm-1) Parameter 191 Ir 11 B 193 Ir 11 B 191 Ir 10 B 193 Ir 10 B T 3 18350. 286(2) 18349. 943(2) B 0. 47235(3) 0. 47204(3) T 2 17791. 129(2) 17790. 787(2) B 0. 47455(2) 0. 47424(3) T 1 17186. 970(2) 17186. 679(2) B 0. 47321(2) 0. 47294(2) T 0 16541. 845(1) 16535. 824(2) B 0. 47336(4) 0. 51860(2) T 0 0. 000 B 0. 51809(4) 0. 56684 ' = 2 " = 3 9

Reduced term value plot of v = 2 level of = 2 and = 3 states of Ir. B 10

Electronic configuration Ir. N Ir. C Ir. B 3 1 2 1 4 2 2 1 3 5 d 6 s 1 2 ? 1 2 1 + , 3 ¯ and 1 1 1 2 1 4 2 2 1 2 Ir There is no = 3 substate from 2 Possible electronic configuration for the ground state of Ir. B 1 2 1 4 2 2 1 1 2 1 (2) 1 2 1 4 2 2 (1) Tentative assignment Ground state X 1 3 1 , 3 , 1 , 3 1 , 3 Excited state [ 16. 5 ] 1 2 2 p B

The (1, 0) band of the ' = 2 – " = 3 transition of Ir. B with partially resolved hyperfine structure Wavenumber (cm-1) 12

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 Atom I (mag. dip. ) 193 Ir 3/2 0. 16 B 3/2 2. 688 We ascribe the large hyperfine interaction to the B atom In case a coupling scheme

For a 1 3 state ( = 3 and = 0) h" = 3 a For a 1 2 state ( = 2 and = 0) h' = 2 a Hyperfine structure Q(3) line Case a F = I + J F 9/2 7/2 5/2 3/2 J=3 1 2 q(F”) 9/2 J=3 7/2 X 1 3 5/2 3/2

The (1, 0) band of the ' = 2 – " = 3 transition of Ir. B with partially resolved hyperfine structure Wavenumber (cm-1) 15

Using linewidth measured from the Q and P branches. The hyperfine constants are estimated to be X 1 3 state [16. 5] 1 2 state h = 0. 0286 cm-1 h = 0. 0116 cm-1

for X 1 3 state for [16. 5] 1 2 state

Summary *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. 18

Acknowledgments This work was supported by grants from the Research Grants Council of the Hong Kong SAR, China (Project No. HKU 7015/04 P) and Committee on Research and Conference Grants, The University of Hong Kong. 19