FOURIER TRANSFORM EMISSION SPECTROSCOPY AND AB INITIO CALCULATIONS ON WO R. S. Ram, Department of Chemistry, University of Arizona J. Liévin, Université Libre de Bruxelles, Laboratoire de Chimie Physique Moléculaire P. F. Bernath, Department of Chemistry, University of York

Transition Metal Containing Molecules The study of transition metal containing molecules provide insight into chemical bonding in simple metal systems. The study of these molecules are also of theoretical importance. Experimental data are needed to test and advance the quality of ab initio calculations. The transition metal containing molecules are also of astrophysical importance. The unpaired d-electrons produce a large number of low-lying electronic states with high spin and large orbital angular momentum. In addition the large spin-orbital interactions result in complex spectra making their analysis difficult. WO is a good example.

Previous Work Weltner & McLeod (1965) Green & Irvin (1981) Vittalachar & Krishnamurthy (1954) Gatterer et al. (1957) Samoilova et al. (1981) Kuzyakov et al. (1997) Kraus et al. (1998) Lorenz et al. (1999) Nelin & Bauschlicher (1985) Ram et al. (2001) [ 3 Σ - ground state] Cooke et al. (2004) [ 3 Σ - ground state] Matrix Isolation Emission and Absorption Laser Spectroscopy SCF and CASSCF Calculations FT Emission Spectroscopy Microwave Spectroscopy

Present Work WO spectra re-investigated in the cm -1 region Ab Initio calculations performed for states below cm -1 Microwave discharge of WCl 6 vapor mixed with 1.9 Torr of He Fourier transform spectrometer of the National Solar Observatory at Kitt Peak UV beam splitter InSb detectorsSuper blue Si Green glass filters Filters: OG530 and CuSO 4 Resolution: cm -1 Resolution: 0.03 cm scans (10 hrs)6 scans each (one hour) , cm cm -1

Observed Bands

Observed Transitions of WO New Group New States Group 1Group 2Group 3 1Σ+1Σ+ 5Π5Π A'2A'2

[7.5]0 + - X0 +, 0-0

D1-X0 +, 0-0 C2-X1, 0-1 D1-X0 +, 1-1 [ 186 WO- 184 WO = cm -1 ]

C1-X0 +, 0-0 Large isotope splitting even in the 0-0 bands [ 186 WO- 184 WO = cm -1 ] Strong isotope dependant interaction in the excited state ?

[a+15.3]0 + - [a+5.1]0 +, 0-0

StatevTvTv BvBv 10 7 × D v 10 4 × q v 2a (29) (52)2.492(31)1.62* 1a (10) (90)2.489(25)1.6207(36) X10a (89)2.485(24)1.6258(55) (31) (72)2.638(22) (20) (65)2.641(20) (15) (56)2.591(16) (86) (53)2.573(14)-- X (54)2.557(15)-- Constants for the X 3 Σ - state q = (γ-2B) 2 /(2λ+γ-2B) λ = ~207 cm -1 ~414 cm -1 X1 X0 +

Constants for Group 1

Constants for Group 2

Constants for Group 3

Const. (cm -1 ) X0 + X1 ωeωe (71) (34) ωexeωexe (40)4.0314(16) ωeyeωeye (60) -- BeBe (60) (31) αeαe (23) (15) r e (Å) (12) (62) Equilibrium constants for the X 3 Σ - state

Ab Initio Results

Summary Emission spectrum of WO has been investigated in the cm -1 region and observed bands have been classified into three groups. First two groups have lower states with Ω=0 + and Ω=1 which have been assigned as the spin components of the X 3 Σ + ground state of WO. Third group consists of seven bands with a band at 9877 cm -1 having its upper state common with the A´2 state of group 2. Some of the lower states of this group are probably the spin components of the predicted 1 5 Π state. The observed 1 Σ + state at 4910 cm -1 is probably the predicted 1 1 Σ + state.

Acknowledgments NASA Laboratory Astrophysics Program UK Engineering and Physical Sciences Research Council (EPSRC)