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Related Concept Videos

UV–Vis Spectroscopy: Woodward–Fieser Rules01:29

UV–Vis Spectroscopy: Woodward–Fieser Rules

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UV–Visible absorption spectra of conjugated dienes arise from the lowest energy π → π* transitions. The light-absorbing part of the molecule is called the chromophore, and the substituents directly attached to the chromophore are called auxochromes. A strong correlation exists between the absorption maxima, λmax, and the structure of a conjugated π system. The Woodward–Fieser rules predict the value of λmax for a given...
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Atomic Absorption Spectroscopy: Atomization Methods01:25

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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...
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Atomic Absorption Spectroscopy: Lab01:21

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For AAS measurements, samples must be introduced as clear solutions, often requiring extensive preliminary treatment to dissolve materials like soils, animal tissues, and minerals. Common methods for sample preparation include treatment with hot mineral acids, wet ashing, combustion in closed containers, high-temperature ashing, or fusion with reagents.
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Atomic Absorption Spectroscopy: Interference01:25

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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.
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UV–Vis Spectroscopy of Conjugated Systems01:32

UV–Vis Spectroscopy of Conjugated Systems

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Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
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Molecular Spectroscopy: Absorption and Emission01:14

Molecular Spectroscopy: Absorption and Emission

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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.
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Related Experiment Video

Updated: Sep 4, 2025

Production and Measurement of Organic Particulate Matter in a Flow Tube Reactor
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Complexities in Modeling Organic Aerosol Light Absorption.

Kyle Gorkowski1, Katherine B Benedict1, Christian M Carrico2

  • 1Earth and Environmental Science, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.

The Journal of Physical Chemistry. A
|July 14, 2022
PubMed
Summary
This summary is machine-generated.

Modeling brown carbon (BrC) light absorption requires understanding its evolving refractive index. New multivariate models improve predictions of BrC

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Related Experiment Videos

Last Updated: Sep 4, 2025

Production and Measurement of Organic Particulate Matter in a Flow Tube Reactor
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Production and Measurement of Organic Particulate Matter in the Harvard Environmental Chamber

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Split Point Analysis and Uncertainty Quantification of Thermal-Optical Organic/Elemental Carbon Measurements

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Area of Science:

  • Atmospheric Chemistry
  • Aerosol Science
  • Radiative Transfer

Background:

  • Aerosol particles undergo dynamic physicochemical transformations in the atmosphere.
  • Current models often use fixed aerosol optical properties, leading to errors in radiative impact assessments.
  • Accurate modeling of aerosol aging and its effect on optical properties is crucial for climate science.

Purpose of the Study:

  • To develop improved multivariate models for predicting the light absorption properties of brown carbon (BrC).
  • To investigate the influence of molecular structure on BrC's complex refractive index.
  • To assess the impact of hygroscopic growth on BrC light absorption.

Main Methods:

  • Developed two multivariate modeling approaches for brown carbon light absorption.
  • Extended existing refractive index modeling frameworks and created a new model based on molecular descriptors (aromatic rings, functional groups).
  • Utilized spectral absorption measurements and hygroscopicity experiments coupled with modeling.

Main Results:

  • The second multivariate model, using molecular descriptors, showed improved agreement with measured spectral absorption peaks of BrC.
  • This new model offers a promising simplification for treating brown carbon optics.
  • Organic functionalities were shown to enhance hygroscopic uptake, leading to increased light absorption.

Conclusions:

  • Multivariate modeling based on molecular structure is effective for predicting brown carbon's complex refractive index and optical properties.
  • Accurate representation of BrC aging and its optical properties is essential for atmospheric radiative transfer.
  • The study highlights the combined importance of BrC's intrinsic optical properties and its interaction with water in the atmosphere.