Ramya Nagarajan, Jie Yang and Dennis J. Clouthier A spectroscopic study of the linear-bent electronic transitions of jet-cooled HBCl and BCl 2 And The electronic spectra of jet-cooled BC

 BCl 2 & HBCl * Reactive intermediates: CVD (BCl 3 (NH 3 /H 2 )) and plasma etching (BCl 3 /Ar ) processess * Spectroscopically interesting: Linear-Bent systems & Renner- Teller effect  BC * Boron carbide (B 4 C): extremely hard, chemically inert, high neutron absorbing cross section * Used in bulletproof vests, nuclear reactor control rods, abrasive for cutting * High resolution gas phase study of B-X and C-X transitions in BC Why study?

BCl 3 /H 2 /Ar B(CH 3 ) 3 /Ar Pulsed valve Ring electrodes BCl 2, HBCl BC Pulsed Discharge Source

Pumping Laser Tunable Dye laser Oscilloscope + Gated integrators Computer PMT Monochromator Experimental Setup

Pump Laser Tunable Dye laser Synchronous-scan LIF Technique PMT Laser: Offset: 450 cm -1

 BCl 2 * Matrix isolation studies: IR spectra showing activity in sym stretch ν 1 and asym stretch ν 3 Hassanzadeh and Andrews, J. Phys. Chem. 97, 4910 (1993) * VUV photoexcitation spectroscopy of BCl 3 : Emissions from BCl 2 in nm and nm region Jochims et al, J. Phys. B: At. Mol. Opt. Phys (1999)  HBCl * Gas phase emission spectra recorded Clouthier et al, J. Am. Chem. Soc. 127, (2005) Background

BCl 2 : 17 valence electrons GS: (a 2 ) 2 (b 2 ) 2 (a 1 ) 1 (b 2 ) 0 : 2 A 1 ES: (a 2 ) 2 (b 2 ) 2 (a 1 ) 0 (b 2 ) 1 : 2 B 1 HBCl: 11 valence electrons GS: (a ” ) 2 (a’) 2 (a’) 1 (a ” ) 0 : 2 A ’ ES: (a ” ) 2 (a’) 2 (a’) 0 (a ” ) 1 : 2 A ” Walsh diagram σ σ σ σ πa" π a' a" σuσu σuσu σgσg σgσg σuσu σgσg πuπu πgπg πuπu a1a1 b1b1 b2b2 b1b1 b2b2 b2b2 b2b2 a1a1 a1a1 a1a1 a2a2 a1a1 <XBX<HBX

v2v2 K=l+              2Π2Π 2A12A < XBX/HBX Renner-Teller effect in Linear-Bent systems

HBCl LIF spectrum A 2 A"П←X 2 A′ system ~ ~

K a " = 0 K a " = 2 K a ' = 1 F(J,K a ) = (A-B)K a 2 + BJ(J+1)  K a = ±1 H 11 B 35 Cl H 10 B 35 Cl ν 2 : HBCl bend ν 3 : BCl stretch Π Σ Emission spectra: HBCl

H 11 B 35 Cl H 10 B 35 Cl ΣΠΣΣΣΠΠΠ Sync-scan LIF: HBCl

BCl 2 LIF spectrum A 2 B 1 П ← X 2 A 1 system ~~

BCl 2 LIF spectrum A 2 B 1 П ← X 2 A 1 system ~~

11 BCl 2 10 BCl 2 Sync-scan LIF: BCl 2 Total LIF

11 B 35 Cl 35 Cl 11 B 35 Cl 37 Cl 11 B 37 Cl 37 Cl 10 B 35 Cl 35 Cl 10 B 35 Cl 37 Cl 10 B 37 Cl 37 Cl ω10ω (24)695.87(24)692.31(37)723.28(41)719.56(42)716.57(29) ω20ω (11)278.81(8)276.74(17)285.13(16)281.84(16)278.46(13) x (6)-3.17(8)-2.87(13)-3.58(11)-3.46(12)-3.15(11) x (2)0.26(1)0.34(3)0.28(2) 0.41(3) x (4)-1.45(4)-1.30(9)-1.59(6)-1.54(7)-1.38(6) Emission spectra: BCl 2 ν 1 : sym stretch ν 2 : bend

 Fourier Transform emission study of B-X transition of BC Bernath et al, J. Chem. Phys. 93, 8482 (1990)  Matrix isolation studies of B-X and C-X transitions Maier et al, J. Phys. Chem A. 102, 9107 (1998)  LIF study of B-X system of BC (MF10) Cheung et al, Chem. Phys. Lett. 16, 509 (2011) B 4 Σ – ← X 4 Σ – cm -1 C 4 Π ← X 4 Σ – cm -1 GS: 3σ 2 4σ 2 5σ 1 1π 2 : X 4 Σ – ES: 3σ 2 4σ 1 5σ 2 1π 2 : B 4 Σ – 3σ 2 4σ 2 5σ 0 1π 2 2π 1 + 3σ 2 4σ 1 5σ 1 1π 2 2π 1 : C 4 Π Boron Carbide

Sync-scan LIF: B 4 Σ - ← X 4 Σ - system

* Feature due to 10 BC Simulated Experimental * * * * B 4 Σ - (b) ← X 4 Σ - (b) : Sync-scan LIF

Spin -splitting

a Bernath et al, J. Chem. Phys. 93, 8482 (1990) Molecular parameters Molecular Constants X4Σ–X4Σ– B4Σ–B4Σ– 11 BC 10 BC 11 BC 10 BC B0B (22) (38) (21) (57) λ0λ a (11) r0r (2)1.4647(3) T 0 ( 11 BC) = (26) T 0 ( 10 BC) = (41)

a Bernath et al, J. Chem. Phys. 93, 8482 (1990) 3σ3σ 4σ*4σ* 5σ5σ 1π1π 3σ3σ 4σ*4σ* 5σ5σ 1π1π Molecular parameters X4Σ–X4Σ– B4Σ–B4Σ– Molecular Constants X4Σ–X4Σ– B4Σ–B4Σ– 11 BC 10 BC 11 BC 10 BC B0B (22) (38) (21) (57) λ0λ a (11) r0r (2)1.4647(3) T 0 ( 11 BC) = (26) T 0 ( 10 BC) = (41)

LIF spectrum: C 4 П ← X 4 Σ - system

Simulated Experimental C 4 П(b) ← X 4 Σ - (b) : Total LIF spectrum

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