Questions tagged [photochemistry]
Photochemistry is a branch of chemistry concerned with the chemical effects of ultraviolet, visible, or infrared radiation.
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Non-radiative decay rates computation
What is the most straightforward computational method to estimate the non-radiative decay rates in organic molecules? I have done TD-DFT calculations and really struggling to compute the rates.
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is it possible to express the threshold energy in photoelectric effect in terms of ionisation energy + something
I was studying the variation of stopping potential with frequency of incident light and wanted to compare this graph for different metals. It's clear to me that if it's easy to unbound an electron ...
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How does the daguerrotype give directly a positive image?
I have read the wikipedia entry about the old photographic process called
daguerrotype.
It says there
The image is on a mirror-like silver surface and will appear either positive or negative, ...
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Ozone from 10um IR?
Ozone is easily produced by Hg lamps with <200nm power (peak@185nm), but O2 also strongly absorbs around 10um. I've poked around but can't find any discussion of ozone production at 10um. Is the ...
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Photochemistry/Physicalchemistry - Fluorescence & Solvent Form
The hint from my instructor for the answer is related to Jablonski Diagram.
The scenario: using fluorometer to measure fluorescence of a compound. How would my fluorescence results differ when ...
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How are these green, blue, and purple markers fluorescing under monochromatic 589nm (yellow) light?
I have some green, blue, and purple markers which clearly fluoresce under monochromatic light with a lower wavelength. Here they are illuminated by 589nm light emitted by a low pressure-sodium lamp (...
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What is the difference between Aluminum Potassium Sulfate and Aluminum Sulfate?
What is the difference between Aluminum Potassium Sulfate and Aluminum Sulfate? I mix my own photography chemistry and a formula calls for Aluminum Potassium Sulfate. My chemical supplier only has ...
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What is the reason of producing *spark* in the volcanic reaction (decomposition of ammonium dichromate)?
In a scientific demonstration of volcanic eruption(decomposition of ammonium dichromate), the green chromium(III) oxide produces an orange spark to mimic the eruption of lava from a volcano.
I would ...
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What chemical(s) in peanut butter cause it to glow under UV light?
It is relatively well known that peanut butter glows in the dark under UV light (if you don't believe me, see this short YouTube demo by NileRed).
I've tried it myself and it is clearly a real thing.
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Why is silver(I) oxide sensitive to a long period exposure to the light?
I will do a reaction where I will use silver oxide as a catalyst (Lewis acid) that will help me to do a nucleophilic substitution. I read that it is photosensitive but I could not find the reason why ...
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Are there tenebrescent minerals like KCl, but ideally resettable with UV/IR?
Is there a ‘simple’ mineral that is tenebrescent (getting reversibly darker on irradiation), but is resettable with UV or IR?
Hackmanite, spodumene and tugtupite (Wikipedia examples for tenebrescence) ...
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What is the probability the bonds broken with sunlight reforming back?
The maximum wavelength $\lambda$ capable of breaking a chemical bond can be estimated as $\lambda = hc/E.$
UV-A $(\pu{380 nm})$ can break bonds with the energy up to $\pu{315 kJ mol^-1},$ UV-B $(\pu{...
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Lifetime components in phosphorescence decay
I'm studying the phosphorescence decay of diacetyl in acetonitrile (it has a high quantum yield of intersystem crossing). The fluorimeter than I'm employing has microsecond resolution and, since the ...
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Graph of kinetic energy of ejected electron vs intensity
While studying photoelectric effect I got a doubt in the graph of kinetic energy of ejected electron vs the intensity of electromagnetic radiation.
Everywhere this graph is given as
But here for 0 ...
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Is there an alternative to potassium iodide as an electrolyte in dye-sensitized solar cells?
I'm helping my son build a dye-sensitized solar cell for his school project according to the directions on homemade-circuits.com. We're currently in the process of gathering the necessary materials. ...
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I have plotted a Stern-Volmer Plot but cannot work out the fluorescence lifetime to be able to get the rate constant [closed]
I have plotted a stern Volmer plot and have my straight line equation. I understand that the gradient is kqtf but I need tf to work out kq but I don't have kd to do 1/kd.
How do I work it out?
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Why is it recommended to not store commercial sodium silicate solutions in direct sunlight, what are the effects of doing so and can it be modelled?
I regularly purchase aqueous sodium silicate solutions from commercial providers for my studies and note that a storage recommendation for all different grades (i.e. differing $\ce{SiO2 / Na2O}$ ...
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Is there any process that converts water into hydrogen and oxygen by using light and a catalyst?
Can water be converted into hydrogen and oxygen using sunlight and a specific catalyst? I can imagine a electrolysis reaction using a catalyst that uses light to release electrons. The goal is to find ...
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Excited states and emission lifetimes
I have some doubts about the nomenclature of the lifetimes. Are singlet and fluorescence lifetimes the same? As well as the triplet and phosphorescence lifetimes?
Also, can the triplet/phosphorescence ...
user78790
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Photoelectric effect: What happens when you irradiate the metal strip with a wave of frequency exactly equal to threshold frequency of the metal?
My teacher said that if we irradiate the metal strip (used in generating the photoelectric effect) with light having frequency equal to the metal's threshold frequency, then the electrons will have ...
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Does zinc oxide lose its UV blocking properties when mixed with oil?
Zinc oxide provides strong protection against UVA and UVB radiation. Does $\ce{ZnO}$ retain this protection when it is dissolved in oil?
When $\ce{NaCl}$ is dissolved in water, the $\ce{Na+}$ and $\ce{...
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Can we make chemical bonds using light, instead of breaking them?
I am trying to bridge a conceptual understanding of how light affects both breaking and forming bonds. When bonds are broken, energy is absorbed (endothermic process). Conversely, when bonds are made, ...
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Two wavelength photo-initiators?
Not a chemist so I hope you'll forgive any amateur mistakes. I found an overview of 3D printing resin photo-initiators here:
https://pubs.acs.org/doi/10.1021/acsapm.8b00165#tbl1
All these activate ...
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How does the size of a molecule subject to photo-isomerization affect it's isometric configuration?
When azobenzene is photo-excited to a higher energy configuration, the electron orbital take new energy levels and position's, changing the over all configuration of the molecule.
Now, if various ...
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Are there any examples of chemiluminescent reaction catalyzed by Group 1/2 metals?
While researching chemiluminescent reaction that normally require enzymes but are replaced with metallic catalysts, as mentioned in this research paper: Direct and Indirect Chemiluminescence: ...
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Which theory could describe rate constant for photodissociation?
I am considering photodissociation reactions and want to find an appropriate theory to describe how one could determine the rate constant. I know Rice-Ramsperger-Kassel-Marcus (RRKM) theory is for ...
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Calculating internal energy of fragment from $D_0$, photon energy and interval energy + velocity of other fragment
I am trying to solve the following:
We consider a photodissociation of a molecule into two fragments. The energy available to the products can be calculated from the bond dissociation energy and the ...
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Why does isolated chlorophyl emits red light?
If we observe isolated chlorophyl solution with UV light, chlorophyl is seen as red. Explanation suggests that when a specific atom of chlorophyl absorbs UV light, the atom gets excited and in a short ...
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Photochemical cycloaddition of ethene
I've got a question regarding the (2pi+2pi)-photocycloaddition of ethene to form cyclobutane. If I understood correctly, the reaction doesn't take place under normal conditions, even if we increase ...
user115162
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What is the reaction steps taken when producing auroral forcing?
As described in here:
https://www.nasa.gov/feature/goddard/2018/sounding-rocket-mission-will-trace-auroral-winds
A mixture of Trimethylaluminium, Barium and Strontium reacts and ionize in the upper ...
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Are there any ways of modifying molecules to increase their probability of two photon absorption?
While checking two photon microscopy, the use of high flux femtosecond laser is required for the dual absorption of photons, due to the low probability of these two photons being absorbed. Is there ...
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How do molecules with opposite rotational photoisomerization bonds behave? [closed]
If a molecules bond change upon isomerization with the respective bonds straining the molecules as they orient themselves opposite from each other, would the molecule undergo some kind of ...
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How can a hydrogen atom ever emit an X-ray photon?
From Scientific American, February 2014:
The Proton Radius Puzzle:
...we had to tune the laser so that it came in with exactly the right amount of energy. The atom would make the jump to the higher ...
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Hydrogen Peroxide & Vinegar Film reversal, can someone help me understand this reaction?
I'm interested in DIY photo development and I came across a reversal process that uses chemicals easily available at the grocery store. The purpose of a reversal process is to take a partially ...
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What is the difference between "primary quantum yield" and quantum yield?
The definition of the primary quantum yield given in Atkins textbook Physical chemistry as "The primary quantum yield, φ, is defined as the number of photophysical or photochemical events that ...
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How to calculate the quantum yield of a photochemical process?
I have that $\pu{100 ml}$ of an aqueous solution containing $\pu{1.0 mM}$ $\ce{H2O2}$, $\pu{100 mM}$ $\ce{CH3OH}$ and $\pu{200 mM}$ DMSO are exposed to monochromatic light with a wavelength of $300$ ...
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Why does increased conjugation in a molecule cause the wavelength absorbed to decrease (i.e. why does a red-shift occur)?
I was recently looking at a paper about novel organic dyes for efficient dye-sensitized solar cells and one point the authors made was that out of the two dyes mentioned the one with a larger pi-...
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Photochemical versus Photophysical
What is the difference between the terms photochemical and photophysical properties? What are some examples from each category?
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question about photodamage on plastic
I know that plastic are susceptible to UV attack. They create free radicals when put under sunlight even when kept for a short time.
I'd like to know if the photo-damage will stop once it is taken ...
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What (non toxic) light sensitive materials do not burn away at high heat?
Specifically related to photoceramics, I am wondering what photosensitive materials exist that can be bonded to glass at high heat in a kiln (a microwave kiln to be more exact).
By non-toxic I mean a ...
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Why does STED microscopy cause photodamage?
STED (stimulated emission depletion) microscopy is a technique which enables sub-diffraction limit of light imaging.
The depletion laser is at 775nm, and about 500 mW, concentrated for a short ...
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What is the role of the Magnesium Ion in Chlorophyll [duplicate]
Chlorophyll as the main photoreceptor molecule in photosynthesis seems to have three unique features 1) a lot of conjugated double bonds, 2) a ring like structure and 3) a central metal ion (Mg). The ...
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What if kinetic energy of ejected electron = 0
When hf ≥ work function, Then the electron still comes out. So, if I say kinetic energy of ejected electron = 0, it should still come out. Right ?
Then, how does the electron even move out or gets ...
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Photoelectric cells
I've read about photoelectric cells, and most of the sources say that Potassium and Cesium can be used as electrodes in the same. But why not Rubidium?
The abundant isotope of Rb (72.2%) is not ...
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Organic Based Photocathode
What organic molecules have a relatively small work function, preferably in the visible spectrum? Polycyclic aromatic hydrocarbons are in the low UV spectrum, making it unsuitable for the photocathode ...
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electronic transition for polyenic molecules
I am having troubles with polyenes states symmetry.
I found an exercise on the pentadien, where they ask us to analyze the symmetry of the singlet excited states corresponding to:
State S1: π+ →π+
...
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Photochemical reduction of benzophenone: why inverted flask?
I've come across an interesting protocol for photochemical reduction of benzophenone to benzhydrol (diphenyl methanol) with sodium alcoholate in alcohol, the 2nd protocol in https://prepchem.com/...
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Does an electron's spin change when being excited?
My preconception is that when you fill an empty orbital by exciting an electron (with a photon), the empty orbital should be filled by an electron with the same spin. However, I've seen examples of ...
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Calculating phosphorescence quantum yield using the given datas' [closed]
A molecular excited state has a fluorescence lifetime of 10 nanoseconds and a phosphorescence life time of 10 microseconds. There are no other processes, what's the phosphorescence quantum yield?
I ...
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Is light a reactant in photochemical reactions?
According to IUPAC a photochemical reaction is a reaction caused by absorption of light. I still can't understand how we should consider light as a part of a reaction. Is a catalyst or a reactant?
In ...
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