1. Lineshape Analysis of Dynamic Rotational Spectra in the Presence of Internal Angular Momentum
Brooks H. Pate, Gordon G. Brown, and Justin L. Neill
Department of Chemistry
University of Virginia

2. Dynamic Rotational Spectroscopy
Rotational Spectroscopy of Highly Vibrationally Excited Molecules
Intramolecular Vibrational Energy Redistribution (IVR) Causes Time-Dependent Molecular Structure
These dynamics lead to frequency modulation effects known in NMR spectroscopy (Dynamic NMR: motional narrowing and coalescence)

3. New Effects Unique to Rotational Motion: Gyroscope Dynamics from Internal Angular Momentum
Methylbutenyne
V3 = 700 cm-1

4. Rotational Transitions MBEY Transition Intensities MBEY
A Sym.
E Sym.
Kr = 0 (Gyro.)
Kr = 0 (Gyro.)
Ka = 0 (Asym.)
Ka = 0 (Asym.)
A Sym.
E Sym.

5. Molecular Parameters for methyl butenyne and butynone
Inertia Ellipsoid for MBEY *
qTOP = 59.2°
Principal Axis (Asymmetric Limit) *
qRAM = 35.7° *
V3 = 706 cm-1 m
r Axis (Gyroscope Limit) *
S.L. Hsu, W.H. Flygare; J. Mol. Spec. 32 (1969) 375.
Inertia Ellipsoid for Butynone m *
qTOP = 62.3°
Principal Axis (Asymmetric Limit) *
qTOP = 36.8° *
V3 = 375 cm-1
r Axis (Gyroscope Limit) *
O.L. Stiefvater, J. Sheridan; Proc. Chem. Soc (Dec.) 368.

7. Coalescence PhenomenonB kr kf
Lifetime Broadening
Frequency Pulling
Coalescence
Narrowing
No Reaction
Increasing Reaction Rate

8. Gyroscope Dynamics
C: Coalescence Parameter

9. Gyroscope Dynamics C: Coalescence Parameter N: Narrowing Parameter
(Friction)

10. Gyroscope Coalescence
E Pentenyne 2D IR – CPFTMW Double Resonance Scan
Gyroscope Coalescence
J = 3 -2
J = 2 - 1

13. Methylbutenyne Dynamic Rotational Spectrum
IR Prepares J=0 Exclusively through P(1) Excitation
J = 1 - 0

14. Vinyl Isocyanate Torsional Potential
Dynamic
Rotational
Spectroscopy
State
mixing
Rigid
rotor
Justin L. Neill: WG08

15. 3164 cm-1 band Monitor 202101 R(1) Laser pumps
all three J = 21 a-type
transitions at once;
population in 101 of GS
is much greater than
that in 111 or 110, so
most of excited population
is in 202

16. Conclusions and Acknowledgements
Intramolecular dynamics can be studied through line shape analysis of the rotational spectra of highly excited molecules
Dynamic spectroscopy effects not limited to geometry changes
Funding: NSF Experimental Physical Chemistry and NSF MRI Program

17. Dynamic Rotational spectrum of molecules with sources of internal angular momentum
Methyl Butenyne
rTOT = 99.8 states/cm-1
rABOVE = 13.5 12
Butynone
rTOT = 31.4 states/cm-1
rABOVE = 12.7