1. Chirped-pulsed FTMW Spectrum of 4-Fluorobenzyl Alcohol
Chirped-pulsed FTMW Spectrum of 4-Fluorobenzyl Alcohol. Structure and Torsional Motions in the Ground Electronic State Phase.
Ryan G. Bird, and David W. Pratt
University of Pittsburgh
Justin L. Neill and Brooks H. Pate
University of Virginia

2. Excited State Spectroscopy
FBA electronic spectrum
4 band caused by internal rotations
Difficult to separate S0 and S1 barriers
Use CP-FTMW to study S0
0.2cm-1

3. Methyl Internal Rotation
Internal rotation cause perturbations
Ĥ = ĤRot + ĤInt
Three types of rotor
High barrier, Low barrier, Asymmetric
Difficulties in assigning spectra1
JB95, SPCAT, XIAM
1Kleiner, I. Journal of Molecular Spectroscopy 2010, 260, 1

4. CP-FTMW Spectrometer MW Synthesizer Arbitrary Waveform Generator
Fourier Transform
Free Induction Decay
Chirped Pulse
240 MHz
500 MHz
Digitizer
(10 Gs/s)

5. o-Toluidine
10000 avg
500 MHz CP

6. High Barrier: o-Toluidine+ -
Ĥ = ĤRot + ĤInt + ĤQuad
ĤRot ›› Ĥint
ĤQuad › Ĥint
Barrier high; Tunneling splitting low
JB95, XIAM, SPFIT
Torsion angle 60
180
300
700 cm-1 E A
Morgan, P. J.; Alvarez-Valtierra, L.; Pratt, D. W. The Journal of Physical Chemistry A 2009, 113,

7. o-Toluidine Constants
A Band
E Band
A (MHz)
(1)
(2)
B (MHz)
(1)
(2)
C (MHz)
(3)
(5)
χaa (MHz)
2.007(7)
2.02(1)
χbb (MHz)
2.05(1)
2.04(2)
χcc (MHz)
-4.06(1)
-4.07(2)
DJ (kHz)
0.35(8)
0.5(1)
DJK (kHz)
-1.4(3)
-2.0(5)
DK (kHz)
-4(4)
-4(7)
dJ (kHz)
0.17(5)
0.26 (7)
dK(kHz)
-0.4(6)
0.5(9)
ΔI (amu Å2)
-3.590
-3.586
Lines 52 53
F = 4←3
10000 avg
10 MHz CP A E
F = 3←2 A E
F = 2←1 A E
F = 2←2 A E

8. m-Toluidine
10000 avg
500 MHz CP

9. Low Barrier: m-Toluidine
Ĥ = ĤRot + ĤInt + ĤQuad
ĤRot ≈ Ĥint
Barrier low; Tunneling splitting high
JB95, XIAM
Torsion angle 60
180
300 A E
9 cm-1
Morgan, P. J.; Alvarez-Valtierra, L.; Pratt, D. W. The Journal of Physical Chemistry A 2009, 113,

10. m-Toluidine Constants
XIAM
A (MHz)
3635.9(1)
B (MHz)
(8)
C (MHz)
(5)
χaa (MHz)
2.3(6)
χbb (MHz)
1.9(6)
χcc (MHz)
-4.2(6)
DJ (kHz)
2(1)
DJK (kHz)
-2(2)
DK (kHz)
-31(12)
dJ (kHz)
0.8(5)
dK(kHz)
23(7)
V3 (cm-1)
4.23(6)
ΔI (amu Å2)
-0.52
Lines 79

11. 4-Fluorobenzyl Alcohol

12. FBA: Asymmetric Rotor 0- 0+ CH2OH rotor results in a 2-fold barrier
Rotor axis is mainly along a-axis
µa and µb-type transitions
ΔE between 0+ and 0- is small
µb-type transitions are Coriolis interactions between levels 0+ 0- 0+ 0- a b

13. FBA Constants FBA LIF1 Benzyl Alcohol2 A 0+ (MHz) 4628.9(20)
(1)
B 0+ (MHz)
928.5(10)
(1)
C 0+ (MHz)
803.1(6)
(5)
A 0- (MHz)
4628.3(15)
(1)
B 0- (MHz)
928.9(10)
(1)
C 0- (MHz)
803.8(10)
(5)
Fab (MHz)
(8)
Fbc (kHz)
57.418(1)
ΔE (MHz)
(2)
1Nikolaev, A. E, In Preparation
2Utzat, K. A.; Bohn, R. K.; Montgomery, J. A.; Michels, H. H.; Caminati, W. The Journal of Physical Chemistry A.

14. Barrier Problems Challenging to measure High Barriers > 500 cm-1
o-toluidine ≈ 700 cm-1
JB 95, SPCAT, XIAM
Challenging to simulate Low Barriers
m-toluidine = 4.2 cm-1
Free rotor limit
Challenging to fit Asymmetric Rotor
FBA: µb and µc >> µa
Coriolis terms have large effect on µb/µc frequencies

15. Acknowledgements Pratt Group: Pate Group:
Dr. David Pratt Dr. Brooks Pate
Justin Young Justin Neill
A.J. Fleisher Matt Muckle
Phil Morgan Daniel Zaleski
Jessica Thomas Amanda Steber
Casey Clements
Patrick Walsh
Dr. Vanessa Vaquero

16. o-Toluidine Constants
Experimental
LIF1
MP2/6-31G+g(d)
A Band
E Band
A (MHz)
(1)
(2)
3230.9(1)
3228.5(1)
B (MHz)
(1)
(2)
2189.0(1)
2189.1(1)
C (MHz)
(3)
(5)
1316.8(1)
1316.9(1)
χaa (MHz)
2.007(7)
2.02(1)
χbb (MHz)
2.05(1)
2.04(2)
χcc (MHz)
-4.06(1)
-4.07(2)
DJ (kHz)
0.35(8)
0.5(1)
DJK (kHz)
-1.4(3)
-2.0(5)
DK (kHz)
-4(4)
-4(7)
dJ (kHz)
0.17(5)
0.26 (7)
dK(kHz)
-0.4(6)
0.5(9)
ΔI (amu Å2)
-3.590
-3.586
-3.51
-3.65
-3.768
Lines 52 53
1Morgan, P. J.; Alvarez-Valtierra, L.; Pratt, D. W. The Journal of Physical Chemistry A 2009, 113,

17. m-Toluidine Constants
Experimental
LIF1
MP2/6-31G**
A Band
E Band
A (MHz)
(4)
3701.3(1)
3700.2(1)
B (MHz)
(4)
1795.9(1)
1795.4(1)
C (MHz)
(4)
1210.4(1)
1210.3(1)
χaa (MHz)
2.18 (5)
χbb (MHz)
2.05(5)
χcc (MHz)
-4.23(5)
DJ (kHz)
0.12(5)
DJK (kHz)
-0.6(1)
DK (kHz)
1.2(5)
dJ (kHz)
0.03(2)
dK(kHz)
0.06(40)
ΔI (amu Å2)
-0.40
-0.414
-0.508
Lines 60
1Morgan, P. J.; Alvarez-Valtierra, L.; Pratt, D. W. The Journal of Physical Chemistry A 2009, 113,