Spectroscopic and Ab Initio Studies of the HBF Free Radical Fumie X. Sunahori and Dennis J. Clouthier Department of Chemistry, University of Kentucky Stuart Carter Department of Chemistry, University of Reading Funding: National Science Foundation

Motivation  Boron trihalides: precursors for chemical vapor deposition and plasma etching processes Aluminum Layer Mask Silicon wafer

Background  # of HBF valence electrons = 11  GS electronic config. [core] (a  ) 2 (a) 2 (a) 1  Nonlinear  ES electronic config. [core] (a  ) 2 (a) 2 (a  ) 1  Linear

Ab Initio Calculations Ground State 2 A'Excited State 2 A" 121° 1.20 Å 1.31 Å1.17 Å1.31 Å Band Origin = 10,104 cm -1 Selection Rules:  J = 0, ±1;  K a = ±1;  K c = 0, ±2 [CCSD(T)/aug-cc-pVTZ]

Production of HBF/DBF Gas Mixture: BF 3 and H 2 /D 2 in Ar

Analysis of Emission Spectra HBF/DBF ExptTheory υ2υ2 993/ /778 υ3υ3 1311/ /1305 F(J,K a ) = (A-B)K a 2 + BJ(J+1) ˉˉ K a " = 0 K a " = 2 K a ' = 1  K a = ±1 4(A-B) - Expt: 78.0(2) cm -1 Theory: 72.4 cm -1 -

Low-Resolution LIF Dissociation to H + BF v = ?? Bond Angle Change 121º to 180º  Transitions to high  2 ' HBF DBF  ??

Theoretical Study of PES  Variational method used to predict rovibrational energy levels in the ground and excited states

Theoretical Study 1.Calculate energies at various geometries [CCSD(T)/aug-cc- pVTZ]: θ = º; r H-B = 0.76 – 1.32 Å; r B-F = 1.02 – 1.42 Å  Potential energy surfaces (PESs) for the X 2 A' and A 2 A" states 2.Fit the data points using a symmetry restricted polynomial expansion 3.RVIB3 program generates rovibronic energy levels by solving the corresponding Schrödinger equation variationally: (Ĥ N + V e + Ĥ SO )|  > = E|  > ˆ

Vibronic Structure

Isotope Shifts (H 10 BF-H 11 BF/ D 10 BF-D 11 BF)

High-Resolution LIF (HBF) Asymmetry Splitting (K  0) N Asymmetry Splitting (K  0) Spin Splitting  K 2 /N Π(0,8,0) - (0,0,0)  (0,7,0) - (0,0,0)

Rotational Analysis Results (HBF/DBF) A(0,7,0) K = 0A(0,8,0) K = 1 B (3) B (7) 10 5 D 1.5(5) A 0.960(6) 10 3 γ 5.5(7) q (1) T (3)T0T (3) Std. Dev AA (8)/ (7) BB (2)/ (3) CC (2)/ (3)  aa  0.161(2)/ 0.097(3) Std. Dev / Ground State Excited State A(0,7,1) K = 0A(0,11,0) K = 2 B (1) B 0.937(1) 10 5 D 1.5 A -0.12(2) 10 3 γ 2.4(13) q 0 T (6)T0T (2) Std. Dev ˜˜ ˜˜ HBF DBF

Molecular Structure X 2 A' HBF ˜ 1.214(2) Å [1.203 Å] (5) Å [ Å] 120.7(1) º [121.1 º] ˜ HCN A 1 A" 125.0º HCO X 2 A' º HNO A 1 A" 116.3º HCF A 1 A" 127.2º HNF A 2 A' 125º ˜ ˜ ˜ ˜

Current Research 1.214(2) Å [1.203 Å] (5) Å [ Å] 120.7(1) º [121.1 º] [1.191 Å] [1.724 Å] [1.190 Å][1.872 Å] [123.3 º] [123.8 º]