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Related Concept Videos

Van der Waals Interactions01:24

Van der Waals Interactions

Atoms and molecules interact with each other through intermolecular forces. These electrostatic forces arise from attractive or repulsive interactions between particles with permanent, partial, or temporary charges. The intermolecular forces between neutral atoms and molecules are ion–dipole, dipole–dipole, and dispersion forces, collectively known as van der Waals forces.Polar molecules have a partial positive charge on one end and a partial negative charge on the other end of the molecule,...
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Atomic Nuclei: Nuclear Relaxation Processes

In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis,  the precessing magnetic moments are randomly oriented around the z-axis. This...
Nuclear Overhauser Enhancement (NOE)01:06

Nuclear Overhauser Enhancement (NOE)

Irradiation of a spin-active nucleus causes an increase or decrease in the signal intensity of neighboring nuclei that are not necessarily chemically bonded or involved in J-coupling. This phenomenon, called the nuclear Overhauser enhancement (NOE), results from through-space interactions between the nuclear spins. The NOE effect decreases with increasing internuclear distance and is generally not observed beyond 4 angstroms. In NOE, dipole-dipole interactions between neighboring spin-active...
¹H NMR: Interpreting Distorted and Overlapping Signals01:02

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Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...

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Related Experiment Video

Updated: Jun 30, 2026

Direct Imaging of Laser-driven Ultrafast Molecular Rotation
10:52

Direct Imaging of Laser-driven Ultrafast Molecular Rotation

Published on: February 4, 2017

Steep atomic dispersion induced by velocity-selective optical pumping.

Alexander Akoulchin1, Mandip Singh, Andrei Sidorov

  • 1Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne, Australia. aakoulchine@swin.edu.au

Optics Express
|October 1, 2008
PubMed
Summary

We developed a new method for creating broadband sign-reversible dispersion in alkali vapor using optical pumping. This technique allows for the control of light

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Gradient Echo Quantum Memory in Warm Atomic Vapor
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Gradient Echo Quantum Memory in Warm Atomic Vapor

Published on: November 11, 2013

Area of Science:

  • Atomic, Molecular, and Optical Physics
  • Quantum Optics
  • Laser Physics

Background:

  • Controlling the speed of light is crucial for applications in quantum information and optical communications.
  • Dispersion, the phenomenon where the speed of light depends on its frequency, plays a key role in light propagation.
  • Alkali vapors offer unique properties for manipulating light due to their atomic structure.

Purpose of the Study:

  • To demonstrate a novel method for preparing broadband sign-reversible dispersion in alkali vapor.
  • To investigate the potential for controlling the group velocity of light using this method.
  • To explore the practical implications for light-speed manipulation in atomic systems.

Main Methods:

  • Utilizing velocity-selective optical pumping to induce specific atomic population distributions.
  • Employing a heterodyne detection method to precisely measure the refractive index in Rubidium (Rb) vapor.
  • Analyzing the spectral characteristics of the dispersion over a 40 MHz region.

Main Results:

  • Successfully prepared broadband sign-reversible dispersion in Rb vapor.
  • Observed that both normal and anomalous dispersion magnitudes remained nearly constant over a 40 MHz spectral range.
  • Achieved significantly reduced (V(g) ≈ c/230) and negative (V(g) ≈ -c/27) group velocities of light.

Conclusions:

  • The demonstrated method provides a robust way to achieve sign-reversible dispersion in alkali vapors.
  • The ability to control light's group velocity, including negative values, opens new avenues for optical technologies.
  • This research contributes to the fundamental understanding and practical application of light-matter interactions.