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Photochemistry is a branch of chemistry concerned with the chemical effects of ultraviolet, visible, or infrared radiation.

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Effective attenuation coefficient for polychromatic light

The Beer-Lambert law gives the optical intensity of collimated light as a function of depth $z$ as: $$I(z)=I_{0}\mathrm e^{-\gamma z},$$ where $\gamma = \alpha + \beta$ is the wavelength-dependent ...
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Why are diagonal arrows disallowed in Jablonski diagrams? [on hold]

My professor mentioned in one of our lectures that diagonal arrows in a Jablonski diagram are disallowed. As far as I know, horizontal arrows signify conservation of energy, while vertical arrows ...
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Efficient ways to make perovskite solar cell crystals

I'm a high schooler involved in a research in which we aim to grow perovskite crystals in microgravity. I've recently come across this article in which they explain how to grow better perovskite ...
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What metals have been used in photography?

I'm interested in knowing about the various processes that have been used in chemical photography. As I understand it, most are based on silver. Are there any major ones which have not used silver? ...
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Do conjugated polymers absorb very low energy photons?

I was reading that in conjugated compounds, the extent of conjugation decides what wavelength photon it can absorb. Longer the conjugation "chain", lesser the photon energy required. So, molecules ...
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Mechanism of photochemical hydroamination with LDA

I've recently come across a couple examples of intramolecular alkene hydroamination accomplished by treatment with LDA followed by visible light irradiation (tungsten light bulb):[1,2] I'd assume ...
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Two-part fluorescence behaviour of DNA oligo tagged with Cy5 fluorophore. Explanations?

We have designed a 56nt single-stranded DNA oligo. Its sequence has no predicted secondary structure, and no predicted reaction with other similar oligos. A Cy5 fluorophore is attached at the 5 prime ...
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81 views

Why does SYBR green emit more signal when bound to DNA?

Principle of SYBR Green SYBR Green I (SG) is an asymmetrical cyanine dye used as a nucleic acid stain in molecular biology. (wiki) This molecule is commonly used in qPCR to meassure the ...
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How much heat is created by absorbent-type sunscreens?

I have a friend who claims her dermatologist told her than sunscreen was what was burning her skin. (I think it's much more likely that her rash/burn was either a sunburn, a skin reaction to some ...
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Photodegradation vs photooxidation

I have been writing a paper about polymers being "aged" by light. Most of this aging happens because light hits atmospheric oxygen and either excites it to its singlet state or causes atmospheric ...
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Does hydrogen peroxide - urea become more active when illuminated?

Dentists' tooth whitening systems and consumer kits use gels containing carbamide peroxide, also known as hydrogen peroxide - urea. Dentists use a light activator: (image from Wikipedia). Consumer ...
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Would the Formation of Benzaldehyde Be Possible Under Specific Conditions?

Our process: We cure an epoxy resin using SLA. The triarylsulfonium hexafluoroantimonate salts in propylene carbonate act as the photoinitiator for the oligomeric reactions between 4,4 ...
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96 views

Maximum (Z) to (E) ratio in the photoisomerization of azobenzene?

Considering the photoswitching of azobenzene, I was told the following argument: Considering that the photoexcited state of azobenzene has a about 50% to 50% chance of yielding either the (E)- or (Z)-...
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117 views

Photochemistry and steady state approximation

I am unsure whether to ask this in physics or chemistry as there is overlap but I am taking this in a chemistry module. System A undergoes photophysical pathways: $$\ce{A + hv -> A\mathrm{*}}$$ $$...
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Are there any (simple) molecules with very different absorption and emission dipole directions?

When a single molecule absorbs or emits light, it does so perpendicular to the direction of the respective transition dipole. In principle, the directions of the dipoles for absorption and emission ...
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When there's a photoelectric effect, do the electrons leave altogether or leave one by one?

When a strong light, or even a laser, hits a metal surface or some molecules, and causes lots of electrons to fly away, do the electrons leave together, or do some of them leave first? If it's the ...
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104 views

Absorption spectrum of Hydrogen molecule in UV region 200 nm - 300 nm (not Atomic Hydrogen)

Can somebody provide Absorption spectrum of Hydrogen molecule? I have searched days for absorption spectrum of Hydrogen molecule in 200 nm - 300 nm UV region and All I got is absorption spectrum of ...
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77 views

How can atoms be influenced by light? [closed]

I was watching a SciShow video "Most dangerous Chemicals". It said that a compound called Azidozide azide explodes on being exposed to light. My question is: how does the the atom feel light. Heat can ...
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62 views

Charge-transfer absorption complex - solvent sensitivity

This is a quote from Anslyn's Physical Organic Chemistry: [...] One way to think of these systems is that the ground state is a weak, intermolecular complex, (D • A). Often such molecules are ...
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What is the range of photon energies can be effectively used to split a diatomic molecule like hydrogen?

I saw photo-ignition of hydrogen-chlorine mixture using UV light on YouTube. Chlorine molecule bond dissociation energy is $\pu{2.51 eV}$ (bluish colour). Bromine molecule bond dissociation energy is ...
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Interpretation of PES spectra

Given that both elements are in the same period, what information from the PES spectra indicates that oxygen would have a smaller atomic radius? (A) The number of peaks (B) The intensity of the ...
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179 views

Is there a catalyst for the decomposition for hydrogen peroxide that speeds it up but still makes the reaction light dependent?

I am building a Rube Goldberg machine for Science Olympiad, and one of the scoring steps is to use light to trigger a chemical reaction, which made me immediately think of the decomposition of ...
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in Chemiluminescence when luminol reacts with hydrogen peroxide, which is an oxidising agent why does the oxygen in the air not oxidise it?

in Chemiluminescence when luminol reacts with hydrogen peroxide, which is an oxidising agent why does the oxygen in the air not oxidise it? because hydrogen peroxide is a compound with an oxygen–...
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Effect of direct exposure to sunlight on various drugs

Today, we were discussing optical activity in class and our teacher said that some drugs are kept in dark coloured bottles to avoid direct exposure to sunlight. Same is the case with some other drugs ...
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Could UV lasers be used to split CO2 and H2O?

I was wondering whether intense UV light, tuned to the correct wavelength, could be used to split carbon dioxide and water molecules as a first step towards synthesizing liquid fuels.
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Is there a connection between UV-degradation and the photoelectric effect

Recently I've been learning about the photoelectric effect in my physics classes. I only have a rudimentary understanding of chemistry, but I've been wondering what the connection is between the ...
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192 views

Finding the wavelength of maximum absorption of Tartrazine using Fieser-Kuhn

How would you use Fieser-Kuhn rules to calculate the wavelength of maximum absorption for tartrazine? Fieser-Kuhn rules states that: $\lambda_{max}=114+5M+n(48-1.7n)-16.5\ R_{endo} - 10\ R_{exo}$ ...
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158 views

Laplacian of the electron density

Is it always the sign of the Laplacian of the electron density a good criterion to decide on the covalent nature of a bond?
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101 views

Excited helium gas from the colision of alpha particles with beta particles?

As alpha particles are made out of 2 protons and 2 neutrons, they are the same as the helium atom with a +2 charge, but with a certain speed. The beta particles are made out of 1 electron at a certain ...
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89 views

Singlet-Triplet energy difference (ΔEST =ES1-ET1) calculation

My research area is computational study of Thermally activated delayed fluorescence (TADF) Materials and their use in Organic light emitting diodes (OLEDs). I want to know why the Singlet-Triplet ...
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131 views

Can 1,2-dioxetanedione (active ingredient in glow sticks) undergo stimulated emission (and thus form a laser)?

In common glowsticks, diphenyl oxalate reacts with hydrogen peroxide, forming 1,2-dioxetanedione. The dioxetanedione is unstable, but direct decomposition to carbon dioxide is a forbidden transition, ...
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What is thermal plasma in-flight oxidation technique?

From Vijay, M.; Ramachandran, K.; Ananthapadmanabhan, P. V.; Nalini, B.; Pillai, B. C.; Bondioli, F.; Manivannan, A.; Narendhirakannan, R. T. Current Applied Physics 2013, 13 (3), 510–516. DOI 10.1016/...
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Hybrid thin films containing azobenzene with reversible photoresponsive behavior

I am going to prepare hybrid thin films containing azobenzene with reversible photoresponsive behavior. I have read about different combinations of inorganic layers such as layered double hydroxide (...
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86 views

Some materials emit more photoelectrons than others - why?

Again, I'm a physicist turning to chemists (so bear with me). So I've been measuring some materials by changing the wavelength of the incident light on the material and I have a detecting tip like in ...
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9answers
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Is it possible for a substance to absorb a longer wavelength of EM wave and emit a shorter wavelength?

I know a fluorescent lamp works my emitting UV first and then the specific substance inside absorbs UV and finally emits visible light. And an object may emit infrared under sunlight due to heating. ...
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Stability of singlet oxygen in various solvents

I wonder which solvent is the best to use as a media for singlet oxygen generation. what is the reason for an increase of singlet oxygen lifetime in deuterated solvents or solvents containg no ...
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Spectra of Methylene Blue

Does the spectrum of Methylene Blue change on prolonged exposure to light? I've studied about the photochemical reactions and about energy transfer reactions. Methylene Blue is a triplet sensitizer ...
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Why photons with longer wave length demonstrate more active scatter and transmit that shorter length?

Why photons with longer wave length demonstrate more active scatter and transmit that shorter length? This troubles me to understand why NIR and Infra-Red goes through diffused media when compared to ...
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How to determine interaction of photon with a hydrocarbon Bixin

Bixin is an apocarotenoid found in annatto with 25 carbons with carboxylic acids at each end of the chain. It is an insoluble orange red pigment. I am interested to study photon interaction with ...
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93 views

Why does a smaller bandgap correlate to increased absorption of visible light?

I am currently involved in a project on metal organic frameworks in my AP chemistry class, and specifically their applications in $\ce{CO2}$ reduction into formate. All the explanations we can find on ...
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182 views

Thermal and photochemical excitation of electron in photochemistry

One of the basic rules of photochemistry is that the electronic configuration of a conjugated polyene does not change when excited thermally, but changes when photochemically excited, i.e. an electron ...
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Is this photochemical [2+2] cycloaddition enantioselective?

How is it deduced that one enantiomer is preferentially formed in the reaction? When I think of the MOs of the reactants, both enantiomers are viable as products.
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Relative energies of singlet and triplet states in Jablonski diagrams

In a Jablonski diagram, we have singlet and triplet excited states where spin is conserved or changed, respectively. My book says any singlet excited state is found to have higher energy than the ...
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242 views

A different type of photosensitive material

I'm curious as to whether there is any small, solid or gel-like material that dissolves/liquefies/evaporates under brief exposure to bright artificial light? So, some small element or agent that would ...
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What might serve as an initial starting photocatalyst for this large water-splitting solar simulator?

The Gizmodo article Insane Light System Blasts the Energy of 10,000 Suns and Phys.org's Let there be light: German scientists test 'artificial sun' both describe the large, powerful concentrated light ...
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87 views

What is the ground state electron configuration of isoprene? [closed]

Also the electron configuration of isoprene at its singlet state and also that of the triplet state?
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83 views

Organic molecules with fast non-radiative decay rates

What structural features in an organic molecule would promote fast non-radiative decay to a ground state, for instance in an aromatic π-conjugated system ?
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Creating Photovoltaic Solar Cells [closed]

I have a friend who recently bought gallium off of Amazon (just for kicks, I have no idea why). I remember seeing that they use a form of gallium to treat photovoltaic solar cells. That got me ...
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What is the difference between a 500W high pressure mercury lamp and a 400W high pressure mercury lamp

I know that the Wattage of a UV lamp is only one factor in the UV output of a light, and therefore cannot be used as a measure of how powerful a light is. Also it doesnt have any effect on the ...
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How to choose a UV lamp for photoisomerization of 4,4'-azobenzene dicarboxylic acid?

I have prepared a thin film containing 4,4'-azobenzene dicarboxylic acid and I want to study the photoresponsive behaviour of them. For the trans-cis isomeration , I used a 365 nm UV LED with ...