Related Concept Videos
01:13¹H NMR: Complex Splitting
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 first.
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 first.
01:30Atomic Emission Spectroscopy: Interference
In atomic emission spectroscopy (AES), high-temperature atomizers excite a broad range of elements and molecules that generate complex emissions from sources such as oxides, hydroxides, and flame combustion products in the flame or plasma. Several strategies can be employed to minimize spectral interferences caused by overlapping emission lines or bands. These include increasing instrument resolution, choosing alternative emission lines, optimally placing the detector in low-background regions,...
01:04¹³C NMR: ¹H–¹³C Decoupling
The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
01:29Mass Spectrometry: Branched Alkane Fragmentation
This lesson delves into the mass spectrometry of branched alkane fragmentation. Branched alkanes possess secondary or tertiary carbon atoms, which generate relatively stable carbocations if the cleavage occurs at the branching point. The high stability of carbocations drives the instant fragmentation of branched alkanes. Accordingly, the branched alkane's molecular ion peak is very weak or invisible in the mass spectra, especially in comparison to a linear alkane.
01:22Atomic Emission Spectroscopy: Instrumentation
The instrumentation of atomic emission spectrometry (AES) involves various components, including atomization devices that convert samples into gas-phase atoms and ions. There are two main types of atomization devices: continuous and discrete atomizers. Continuous atomizers, like plasmas and flames, introduce samples in a constant stream, while discrete atomizers inject individual samples using syringes or autosamplers. The most common discrete atomizer is the electrothermal atomizer.
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Related Experiment Video
Updated: Jun 19, 2026
08:51
Coulomb Explosion Imaging as a Tool to Distinguish Between Stereoisomers
Published on: August 18, 2017
[Measurement of fine-structure branching ratios for Rb-He optical collisions].
1School of Physics Science and Technology, Xinjiang University, Urumqi 830046, China. lvleihxl@163.com
Guang Pu Xue Yu Guang Pu Fen Xi = Guang Pu
|October 6, 2009
Summary
Optical collisions between rubidium and helium atoms create distinct fine-structure distributions in rubidium. Branching ratios vary significantly based on laser detuning, with red-wing excitation yielding large, detuning-independent branching.
Area of Science:
- Atomic, Molecular, and Optical Physics
- Quantum Chemistry
- Spectroscopy
Context:
- Investigates optical collisions between rubidium (Rb) and helium (He) atoms.
- Focuses on the Rb(5S1/2) + He + hν → Rb(5P(J)) + He process.
- Utilizes pulsed laser excitation tuned to the wings of Rb resonance transitions.
Purpose:
- To experimentally determine branching ratios in the fine-structure levels of the Rb 5P multiplet resulting from optical collisions with He.
- To measure the relative cross-section for scattering into different fine-structure states (5P1/2 and 5P3/2).
- To analyze the sensitivity of branching ratios and cross-sections to interatomic potentials and nonadiabatic effects.
Summary:
- Branching ratios (n1/n2 for 5P1/2 and 5P3/2 states) were measured using time-integrated intensities of Rb emission lines (I(D2) and I(D1)).
- Detuning from Rb resonance transitions (±200 cm⁻¹) revealed distinct branching behaviors: a detuning-dependent limit of 0.2 in the blue wing and a large, detuning-independent ratio of ~40 in the red wing.
- A fine-structure changing cross-section of (1.1 ± 0.3) × 10⁻¹⁷ cm² was determined from wing excitation, consistent with resonant excitation results.
Impact:
- Provides experimental data on state-selective collision dynamics in atom-light-atom interactions.
- Demonstrates the significant influence of interatomic potentials and nonadiabatic effects on dissociation pathways.
- Offers insights into controlling atomic fine-structure distributions through tailored optical excitation.