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Related Concept Videos

Hess's Law03:40

Hess's Law

There are two ways to determine the amount of heat involved in a chemical change: measure it experimentally, or calculate it from other experimentally determined enthalpy changes. Some reactions are difficult, if not impossible, to investigate and make accurate measurements for experimentally. And even when a reaction is not hard to perform or measure, it is convenient to be able to determine the heat involved in a reaction without having to perform an experiment.
¹H NMR of Labile Protons: Deuterium (²H) Substitution00:48

¹H NMR of Labile Protons: Deuterium (²H) Substitution

This lesson illustrates the role of deuterium substitution in simplifying the NMR spectrum of compounds comprising labile protons. One method employed is the use of deuterium. Amongst the three isotopes of hydrogen, deuterium (2H) has a nucleus composed of one proton and one neutron. When the D2O solvent is added to a pure dry ethanol solution, its labile proton is substituted with deuterium.
Atomic Emission Spectroscopy: Interference01:30

Atomic 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,...
IR Spectrum Peak Broadening: Hydrogen Bonding01:23

IR Spectrum Peak Broadening: Hydrogen Bonding

The vibrational frequency of a bond is directly proportional to its bond strength. As a result, stronger bonds vibrate at higher frequencies, while weaker bonds vibrate at lower frequencies. The stretching vibration of the strong O–H bond in alcohols and phenols (very dilute solution or gas phase) appears as a sharp peak at 3600–3650 cm−1.
However, the extent of hydrogen bonding influences the observed stretching frequency and band broadening. Intermolecular or intramolecular hydrogen bonding...
IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration01:16

IR 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...
Interaction of EM Radiation with Matter: Spectroscopy01:12

Interaction of EM Radiation with Matter: Spectroscopy

Electromagnetic (EM) radiation can be considered an oscillating electric and magnetic field propagating through a medium that can interact with matter in its path. The electric field in the radiation can interact with electrical charges in the atoms or molecules in the matter. On the other hand, the magnetic field can interact with the magnetic field in the atomic nucleus. The study of the interaction between electromagnetic radiation and matter is termed spectroscopy. Spectroscopy is the study...

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Related Experiment Video

Updated: Jul 19, 2026

Analyzing Protein Dynamics Using Hydrogen Exchange Mass Spectrometry
11:37

Analyzing Protein Dynamics Using Hydrogen Exchange Mass Spectrometry

Published on: November 29, 2013

H3+ in the diffuse interstellar medium.

Harvey S Liszt1

  • 1National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA. hliszt@nrao.edu

Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
|October 4, 2006
PubMed
Summary

A faster ionization rate is needed to explain hydrogen molecule abundances in interstellar clouds. Current models struggle with complex trace species, suggesting a need for more advanced theories.

Area of Science:

  • * Astrochemistry
  • * Interstellar Medium Physics

Background:

  • * Diffuse interstellar clouds host hydrogen molecules (H2, HD, H3+).
  • * Existing models struggle to fully explain observed abundances.
  • * Static equilibrium frameworks require modification for observed species.

Purpose of the Study:

  • * To investigate the ionization requirements for observed hydrogen-bearing molecules.
  • * To evaluate the adequacy of current models for interstellar chemistry.
  • * To identify limitations in explaining trace species abundances.

Main Methods:

  • * Analysis of observational data for H2, HD, and H3+.
  • * Application of static equilibrium frameworks for interstellar chemistry.
  • * Time-dependent modeling of hydrogen molecule formation and ionization.

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Defining Hsp33's Redox-regulated Chaperone Activity and Mapping Conformational Changes on Hsp33 Using Hydrogen-deuterium Exchange Mass Spectrometry
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Defining Hsp33's Redox-regulated Chaperone Activity and Mapping Conformational Changes on Hsp33 Using Hydrogen-deuterium Exchange Mass Spectrometry

Published on: June 7, 2018

Related Experiment Videos

Last Updated: Jul 19, 2026

Analyzing Protein Dynamics Using Hydrogen Exchange Mass Spectrometry
11:37

Analyzing Protein Dynamics Using Hydrogen Exchange Mass Spectrometry

Published on: November 29, 2013

Defining Hsp33's Redox-regulated Chaperone Activity and Mapping Conformational Changes on Hsp33 Using Hydrogen-deuterium Exchange Mass Spectrometry
10:24

Defining Hsp33's Redox-regulated Chaperone Activity and Mapping Conformational Changes on Hsp33 Using Hydrogen-deuterium Exchange Mass Spectrometry

Published on: June 7, 2018

Main Results:

  • * A pervasive ionization source, ~10 times faster than cosmic rays, is required.
  • * Observed abundances of H2, HD, and H3+ are generally accommodated with this modification.
  • * Simple equilibrium models fail to explain most trace species.

Conclusions:

  • * Current models need revision to include enhanced low-level ionization.
  • * The complexity of interstellar chemistry necessitates more sophisticated theoretical approaches.
  • * Further research is required to fully understand diffuse interstellar cloud chemistry.