Related Experiment Video
Updated: Feb 24, 2026
08:22
Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
Published on: August 6, 2018
7.4K
Multielectron Effects in the Strong Field Sequential Ionization of Aligned CH3I Molecules
Sizuo Luo1, Wenhui Hu1, Jiaqi Yu1
1Institute of Atomic and Molecular Physics, and Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy, Jilin University , Changchun 130012, China.
The Journal of Physical Chemistry. A
|August 18, 2017
Summary
Strong laser fields drive sequential ionization in methyl iodide (CH3I) molecules. Ionization pathways depend on laser polarization relative to molecular orientation, differentiating parent and fragment ion generation.
Area of Science:
- Physical Chemistry
- Molecular Physics
- Quantum Optics
Background:
- Understanding strong field ionization dynamics is crucial for controlling molecular reactions.
- Methyl iodide (CH3I) serves as a model system for studying molecular ionization due to its symmetric-top structure.
Purpose of the Study:
- To investigate the strong field sequential ionization of CH3I molecules.
- To elucidate the relationship between molecular alignment, laser polarization, and ionization pathways.
- To analyze multielectron release dynamics during Coulomb explosion.
Main Methods:
- Femtosecond laser-induced impulsive alignment.
- Time-of-flight mass spectrometry.
- Measurement of alignment- and angular-dependent ion yields.
Main Results:
- Maximum ionization observed when probe laser polarization is perpendicular to the molecular internuclear axis.
- Fragment ion signals peak when probe laser polarization is parallel to the internuclear axis.
- Ion angular distributions reveal distinct pathways for π- and σ-orbital ionization, correlating with parent and fragment ion generation, respectively.
- Analysis of time-evolved signals of multicharged iodine ions (I^n+, n=1-4) provides insights into sequential multielectron release.
Conclusions:
- The study establishes a clear link between molecular orientation, laser polarization, and specific ionization channels in CH3I.
- Distinct ionization mechanisms for parent and fragment ions are identified based on orbital type (π vs. σ).
- Sequential multielectron dynamics in Coulomb explosion are characterized, offering a deeper understanding of molecular fragmentation under strong fields.
Related Concept Videos
01:21Chemical Ionization (CI) Mass Spectrometry
1.6K
The molecular ion peak of a molecule in the mass spectrum provides vital information for molecular identification. However, conventional electron impact ionization can lead to the rapid dissociation of some molecular ions before they reach the detector. A milder ionization method is required to increase the lifetime of such ionized analyte molecules. Chemical ionization (CI) is a gas-phase protonation reaction useful for mass-analyzing analyte molecules that are easily protonated to yield the...
1.6K
01:27π Electron Effects on Chemical Shift: Overview
1.7K
An applied magnetic field causes loosely bound π-electrons in organic molecules to circulate, producing a local or induced diamagnetic field over a large spatial volume. As the molecules tumble in solution, the field generated by π-electrons in spherical substituents results in a zero net field. However, the net field generated by π-electrons in non-spherical substituents is not zero. The effect of this induced field depends on the orientation of the molecule with respect to B0,...
1.7K
01:13¹H NMR: Complex Splitting
2.0K
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
2.0K
01:19Mass Analyzers: Common Types
1.7K
The quadrupole mass analyzer consists of four cylindrical metal rods arranged in a diamond carrying a DC voltage and a radio-frequency AC voltage. The motion of ions through the quadrupole depends on the field strength, causing only ions of a certain m/z to resonate successfully and strike the detector at a given field strength. Though the transmission rate for these analyzers is high, the exact elemental composition of the sample is not determined because of low resolution; however, they are...
1.7K
01:15Mass Spectrometry of Amines
5.5K
In mass spectroscopy, amines undergo fragmentation to give parent ions with odd molecule weights. This observed mass spectrum follows the nitrogen rule; a molecule with an odd number of nitrogen atoms produces a molecular ion with an odd molecular weight. Amines undergo fragmentation through α cleavage, producing nitrogen-containing cations—iminium ions—and alkyl radicals. Mass spectra of aromatic and cyclic aliphatic amines exhibit strong molecular ion peaks, but acyclic...
5.5K
01:27Inductive Effects on Chemical Shift: Overview
2.3K
The protons in unsubstituted alkanes are strongly shielded with chemical shifts below 1.8 ppm. Methine, methylene, and methyl protons appear at approximately 1.7, 1.2 and 0.7 ppm, while the proton signal from methane appears at 0.23 ppm. An electronegative substituent, such as chlorine, withdraws the electron density from the protons, increasing their chemical shift. Progressive substitution of the hydrogens in methane by chlorine shifts the proton signals increasingly downfield, to 3.05 ppm in...
2.3K