Related Experiment Video
Updated: Jul 18, 2026
10:25
Sub-nanometer Resolution Imaging with Amplitude-modulation Atomic Force Microscopy in Liquid
Published on: December 20, 2016
Watching vibrational energy transfer in liquids with atomic spatial resolution
Zhaohui Wang1, Andrei Pakoulev, Dana D Dlott
1School of Chemical Sciences, University of Illinois at Urbana-Champaign, Box 01-6 CLSL, 600 South Mathews Avenue, Urbana, IL 61801, USA.
Science (New York, N.Y.)
|June 22, 2002
Summary
Vibrational energy moves through molecules via intervening groups, like CH2, in a step-wise manner. Longer pathways increase energy transfer time, with each CH2 group adding about 0.4 picoseconds.
Area of Science:
- Physical Chemistry
- Molecular Dynamics
- Spectroscopy
Background:
- Vibrational energy transfer is crucial for understanding molecular dynamics in liquids.
- Tracking energy flow within molecules provides insights into chemical processes.
Purpose of the Study:
- To investigate the mechanism and kinetics of vibrational energy transfer through alkyl chains in alcohols.
- To quantify the influence of molecular structure on energy dissipation pathways.
Main Methods:
- Utilized ultrafast spectroscopy with mid-infrared laser pulses to excite specific vibrational modes (OH stretching).
- Monitored the temporal evolution of energy transfer across intervening methylene (CH2) and methyl (CH3) groups.
Main Results:
- Observed directional vibrational energy transfer from excited OH groups towards terminal CH3 groups.
- Demonstrated that energy transfer progresses through sequential CH2 units in a step-wise energetic fashion.
- Quantified a linear increase in energy transfer time with the number of CH2 groups, approximately 0.4 picoseconds per group.
Conclusions:
- The length of the intervening alkyl chain significantly modulates the rate of vibrational energy transfer.
- Ultrafast spectroscopy provides a powerful tool to map energy flow pathways within complex molecules.
- Understanding these energy transfer dynamics is key for designing molecules with specific energy dissipation properties.
Related Concept Videos
01:11Atomic Nuclei: Larmor Precession Frequency
The earth's gravitational field produces a 'twisting force' perpendicular to the angular momentum of a spinning mass (such as a spinning top) that causes the mass to 'wobble' around the gravitational field axis in a phenomenon called precession. Similarly, the magnetic moment (μ) of a spinning nucleus precesses due to an external magnetic field directed along the z-axis. The precession of the magnetic moment vector about the magnetic field is called Larmor precession, and the angular frequency...
01:14Molecular Spectroscopy: Absorption and Emission
Molecules possess discrete energy levels called quantum states. Unlike atoms, which have simpler energy levels, molecules possess additional rotational and vibrational energy levels. Each energy level is separated by an energy gap, with the gaps between adjacent electronic, vibrational, and rotational levels varying significantly. The three types of energy levels in a diatomic molecule are shown in Figure 1.
01:24IR Spectroscopy: Molecular Vibration Overview
When Infrared (IR) radiation passes through a covalently bonded molecule, the bonds transition from lower to higher vibrational levels. The fundamental vibrational motions that result in infrared absorption can be classified as stretching or bending vibrations.
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
01:16IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration
A covalently bonded heteronuclear diatomic molecule can be modeled as two vibrating masses connected by a spring. The vibrational frequency of the bond can be expressed using an equation derived from Hooke's law, which describes how the force applied to stretch or compress a spring is proportional to the displacement of the spring. In this case, the atoms behave like masses, and the bond acts like a spring.
According to Hooke's law, the vibrational frequency is directly proportional to the...
According to Hooke's law, the vibrational frequency is directly proportional to the...
01:25Atomic Absorption Spectroscopy: Atomization Methods
Atomic Absorption Spectroscopy (AAS) atomizes samples through flame atomization or electrothermal atomization. Flame atomization typically involves a nebulizer and spray chamber assembly to combine the sample with a fuel–oxidant mixture, creating a fine aerosol mist that enters a burner. Typically, the fuel and oxidant are combined in an approximately stoichiometric ratio. However, for atoms that are easily oxidized, a fuel-rich mixture may be more advantageous. Only about 5% of the aerosol...
01:25Atomic Absorption Spectroscopy: Interference
Interference leads to systematic error in atomic absorption (AA) measurements by enhancing or diminishing the analytical signal or the background. These interferences can be grouped into three main categories: spectral interference, chemical interference, and physical interference.
Spectral interference occurs when signals from other elements or molecules overlap with the analyte signal, falsely elevating or masking the analyte's absorbance. This interference can be corrected using Zeeman,...
Spectral interference occurs when signals from other elements or molecules overlap with the analyte signal, falsely elevating or masking the analyte's absorbance. This interference can be corrected using Zeeman,...