Related Experiment Video
Updated: Jul 19, 2026
10:42
Infrared Degenerate Four-wave Mixing with Upconversion Detection for Quantitative Gas Sensing
Published on: March 22, 2019
Quantum control of internal conversion in 24-vibrational-mode pyrazine
P S Christopher1, M Shapiro, P Brumer
1Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada.
The Journal of Chemical Physics
|October 4, 2006
Summary
Quantum control precisely manipulates internal conversion in pyrazine molecules. This study demonstrates suppressing or accelerating the S(2)-->S(1) transition using a novel quantum dynamics algorithm.
Area of Science:
- Quantum dynamics
- Molecular spectroscopy
- Chemical physics
Background:
- Internal conversion is a key non-radiative decay pathway in molecules.
- Controlling ultrafast molecular processes like internal conversion is crucial for advanced applications.
Purpose of the Study:
- To demonstrate quantum control over the S(2)-->S(1) internal conversion in pyrazine.
- To investigate the role of overlapping resonances in achieving this control.
Main Methods:
- Utilized a complete 24-mode dimensionality model of pyrazine.
- Employed the "QP algorithm" for accurate projected quantum dynamics computations.
- Introduced new diagnostics to analyze resonance contributions.
Main Results:
- Achieved active control, suppressing internal conversion for 50-100 fs (longer than natural ~20 fs).
- Demonstrated acceleration of internal conversion to under 5 fs.
- Showcased superior control in full dimensionality compared to reduced models.
Conclusions:
- Quantum control is effective in manipulating pyrazine's internal conversion.
- Overlapping resonances significantly contribute to successful quantum control.
- Full dimensionality models provide a more accurate representation for enhanced control.
Related Concept Videos
00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
01:25Deactivation Processes: Jablonski Diagram
Luminescence, the emission of light by a substance that has absorbed energy, is a process that involves the interaction of molecules with light. The energy-level diagram, or Jablonski diagram, is a graphical representation of these interactions, illustrating the various states and transitions a molecule can undergo. In a typical Jablonski diagram, the lowest horizontal line represents the ground-state energy of the molecule, which is usually a singlet state. This state represents the energies...
01:26Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
01:16UV–Vis Spectroscopy: Molecular Electronic Transitions
In Ultraviolet–Visible (UV–Vis) spectroscopy, the absorption of electromagnetic radiation is used to probe the electronic structure of molecules. This technique provides insights into molecular electronic transitions, particularly the movement of electrons between different molecular orbitals. Radiation is absorbed if the energy of the electromagnetic radiation passing through the molecule is precisely equal to the energy difference between the excited and ground states. During this process,...
01:15¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
01:21IR Absorption Frequency: Hybridization
Hydrocarbons such as alkanes, alkenes, and alkynes show characteristic C–H stretching absorption bands. These IR stretching frequencies depend on the hybridization of the involved carbon atom and can be explained in terms of the s character of each hybridized atomic orbital.
Among the sp, sp2, and sp3 hybridized orbitals, sp orbitals have the maximum s character (50%). Consequently, the electrons are held more closely to the nucleus, resulting in stronger and shorter C–H bonds that stretch at a...
Among the sp, sp2, and sp3 hybridized orbitals, sp orbitals have the maximum s character (50%). Consequently, the electrons are held more closely to the nucleus, resulting in stronger and shorter C–H bonds that stretch at a...