A spectroscopic study of the linear-bent electronic
transitions of jet-cooled HBCl and BCl2
And
The electronic spectra of jet-cooled BC
Ramya Nagarajan, Jie Yang and Dennis J. Clouthier
Why study?
BCl2 & HBCl
* Reactive intermediates: CVD (BCl3(NH3/H2)) and plasma
etching (BCl3/Ar ) processess
* Spectroscopically interesting: Linear-Bent systems & RennerTeller effect
BC
* Boron carbide (B4C): 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
Pulsed Discharge Source
BCl3/H2/Ar
BCl2, HBCl
BC
B(CH3)3/Ar
Pulsed valve
Ring electrodes
Experimental Setup
Pumping Laser
Tunable Dye laser
Monochromator
PMT
PMT
Computer
Oscilloscope +
Gated integrators
Synchronous-scan LIF Technique
Pump Laser
PMT
Tunable Dye laser
cm-1
Laser:
24000
23000
22000
21000
20000
19000
18000
17000
16000
15000
Offset:
450 cm-1
Background
BCl2
* Matrix isolation studies: IR spectra showing activity in sym
stretch ν1 and asym stretch ν3
Hassanzadeh and Andrews, J. Phys. Chem. 97, 4910 (1993)
* VUV photoexcitation spectroscopy of BCl3: Emissions from
BCl2 in 400-650nm and 200-500nm region
Jochims et al, J. Phys. B: At. Mol. Opt. Phys. 32. 2569 (1999)
HBCl
* Gas phase emission spectra recorded
Clouthier et al, J. Am. Chem. Soc. 127, 10814 (2005)
Walsh diagram
BCl2: 17 valence electrons
HBCl: 11 valence electrons
b2
a'
a1
σu
σ
σg
πu
π
a"
b1
b2
a2
b2
a' a'
a1
πg
a1
b1
a1
πu
σu
σg
a1
b2
σg
σu
<XBX
GS: (a2)2 (b2)2 (a1)1 (b2)0 : 2A1
ES: (a2)2 (b2)2 (a1)0 (b2)1 : 2B1
π
a"
a'
a'
σ
σ
σ
a'
<HBX
GS: (a”)2 (a’)2 (a’)1 (a”)0 : 2A’
ES: (a”)2 (a’)2 (a’)0 (a”)1 : 2A”
Renner-Teller effect in Linear-Bent systems
K=l+
v2
0
2
3
S
D
G
4
G
2
0
D
S
P
1
2
3
F
F
1
P
2Π
0
2A
1
1
0
0
180
160
140 120 100
<XBX/HBX
2
1
S
D
D
S
P
P
HBCl LIF spectrum
A~2A"П←X~2A′ system
14000
14500
15000
15500
-1
WAVENUMBER (cm )
16000
16500
Emission spectra: HBCl
00
31
21
 
02
H11B35Cl
ν2 : HBCl bend
ν3 : BCl stretch
F(J,Ka) = (A-B)Ka2 + BJ(J+1)
Σ
Ka' = 1
 
DKa = ±1
Π
00
21 31
H10B35Cl
Ka" = 2
Ka" = 0
0
500
1000
1500
2000
-1
WAVENUMBER (cm )
2500
Sync-scan LIF: HBCl
Σ
Π
Σ
Π
Σ
Π
Σ
Π
H11B35Cl
H10B35Cl
13000
14000
15000 16000 17000 18000
-1
WAVENUMBER (cm )
19000
20000
BCl2 LIF spectrum
~2A system
A~2B1П ← X
1
16000
18000
20000
-1
WAVENUMBER (cm )
22000
BCl2 LIF spectrum
~2A system
A~2B1П ← X
1
16000
18000
20000
-1
WAVENUMBER (cm )
22000
Sync-scan LIF: BCl2
Total LIF
11BCl
2
10BCl
2
19000
19500
20000
20500
21000
-1
WAVENUMBER (cm )
21500
22000
Emission spectra: BCl2
ν1: sym stretch
ν2 : bend
10
11
35
B Cl2
35
B Cl2
11
12
21
21
22
11 22
23
22
1123
12 23
0
500
1000
11
12 22 13
11 21
1500
2000
2500
0
11B37Cl37Cl
25
26
10B35Cl35Cl
27
24
500
1000
1500
-1
WAVENUMBER (cm )
WAVENUMBER (cm )
11B35Cl37Cl
1122
23
-1
11B35Cl35Cl
1121
10B35Cl37Cl
2000
10B37Cl37Cl
ω10
700.17(24) 695.87(24) 692.31(37) 723.28(41) 719.56(42) 716.57(29)
ω20
282.81(11) 278.81(8)
276.74(17) 285.13(16) 281.84(16) 278.46(13)
x110 -3.28(6)
-3.17(8)
-2.87(13)
-3.58(11)
-3.46(12)
-3.15(11)
x220 0.25(2)
0.26(1)
0.34(3)
0.28(2)
0.28(2)
0.41(3)
x120 -1.55(4)
-1.45(4)
-1.30(9)
-1.59(6)
-1.54(7)
-1.38(6)
Boron Carbide
 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)
GS: 3σ24σ25σ11π2 : X4Σ–
ES: 3σ24σ15σ21π2 : B4Σ–
3σ24σ25σ01π22π1 + 3σ24σ15σ11π22π1 : C4Π
B4Σ–← X4Σ– 17900 cm-1
C4Π ← X4Σ– 34000 cm-1
Sync-scan LIF:
4
4
B Σ ←X Σ
system
11
10
BC+ BC
11
0-0
BC
1-1
2-2
3-3
10
17800
18000
18200
-1
WAVENUMBER (cm )
BC
18400
B4Σ-(b)←X4Σ-(b) : Sync-scan LIF
R(N)
P(N)
11
9
7
5
3
1
0
2
4
6
8
10
Experimental
** **
Simulated
* Feature due to 10BC
17880
17895
17910
-1
WAVENUMBER (cm )
17925
17940
Spin -splitting
44
17920
55
17922
66
17924
-1
WAVENUMBER (cm )
17926
R1(N)+R4(N)
R2(N)+R3(N)
Molecular parameters
Molecular Constants
B0
λ0
r0
X4Σ–
11
BC
1.31119(22)
0.0282a
B4Σ–
10
BC
1.37957(38)
1.4963(2)
T0 (11BC) = 17904.8966(26)
T0 (10BC) = 17906.2710(41)
a
Bernath et al, J. Chem. Phys. 93, 8482 (1990)
11
BC
1.36811(21)
-0.0050(11)
10
BC
1.44023(57)
1.4647(3)
Molecular parameters
Molecular Constants
B0
λ0
X4Σ–
11
BC
1.31119(22)
0.0282a
B4Σ–
10
11
BC
1.37957(38)
BC
1.36811(21)
-0.0050(11)
1.4963(2)
r0
T0 (10BC) = 17906.2710(41)
a
Bernath et al, J. Chem. Phys. 93, 8482 (1990)
1π
1π
X4Σ–
BC
1.44023(57)
1.4647(3)
T0 (11BC) = 17904.8966(26)
5σ
5σ
4σ*
4σ*
3σ
3σ
B4Σ–
10
LIF spectrum:
4
4
C П←X Σ
system
0-0
0-2
0-3
0-1
0-4
0-5
1-0
0-0
1-3
1-4
1-5
1-1
1-6
1-2
0
1-0
33500
34000
2000
4000
6000
-1
WAVENUMBER (cm )
34500 35000 35500 36000
-1
WAVENUMBER (cm )
36500
8000
37000
4
4
C П(b)←X Σ (b):
Total LIF spectrum
Experimental
Simulated
34300 34310 34320 34330 34340 34350 34360 34370
-1
WAVENUMBER (cm )
THANK YOU!