Chemistry Stack Exchange
Chemistry Stack Exchange

Questions tagged [photochemistry]

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

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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 by emitting UV first and then the specific substance inside absorbs UV and finally emits visible light. An object may emit infrared under sunlight due to heating. But those examples are absorbing short wavelength of…
Gstestso
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Do materials exist that absorb Visible light and emit Near InfraRed light?

I am thinking about the possibility of making a hat or other clothing item that might show up funny on cameras, as they are more sensitive to infrared light than human eyes. Therefore, I was wondering if there are any (non hazardous) materials that…
Qqwy
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Mechanism of photolysis of HX

What is the mechanism for the photolysis of $\ce{HX}$ to dihydrogen and dihalogen ? From the low quantum yield (0.3% for $\ce{HI}$ according to one paper) it seems unlikely to be a chain process but I am not sure why it would not be.
J. LS
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Is a triplet state or singlet state more stable?

Is a triplet state or singlet state more stable? How can an atom have a long lifetime in a triplet state even though two electrons have the same spin?
vamsi
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What makes an X-ray machine's white photographic film go black?

I read on a bbc gcse bitesize webpage "In older X-ray machines, white photographic film" [edit- I now know that bbc webpage is wrong, and it's not a white film. I'll leave the rest of the post after the next sentence, as is, but note that from the…
barlop
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Does quantum yield of reaction factor in number of electrons needed?

Can someone tell me if quantum yield of a reaction factors in the number of electrons needed to create the particular species? If not, is there a metric that does? For example, I have a 4 electron reduction which means that even if I have 100%…
Coherent
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What is the explanation of the energy gap law in radiationless transitions?

The rate of radiationless transitions such as internal conversion and intersystem crossing decrease with the size of the energy gap between the states, according to $$k\propto \exp\left(\frac{-\gamma\Delta E}{\hbar\omega_M}\right)$$ The papers by…
J.L.
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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 radioactive either, and is actually quite stable. The…
Buckbitter Inning
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Material that absorbs only in NIR and emits in visible

This Thorlabs VRC4 card here uses a material that absorbs only NIR and emits in visible. The spec sheets don't list what chemical this is. Do you know materials that show similar emission properties even with weak laser excitation?
user1155386
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Kinetics energy expression of photon

I need to calculate the kinetics energy of a photon and I'm trying to deduce a correct expression for calculating it. So we have that $K= \frac{1}{2} m_fv_f^2$ So $v_f= c$ For De Broglie equation we have that $m_f = \frac{h}{\lambda c}$ And then…
Granger Obliviate
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No. of photoelectrons vs frequency and intensity

We know that when the intensity of incident light increases, number of photoelectrons ejected increases irrespective of the frequency (assuming it to be greater than threshold frequency. But does it depend on frequency too in some situations like in…
Aditi Narware
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UV-Vis emission from charge-separated states?

Are there examples of UV-Vis emission from charge-separated states? The cases I have encountered have only absorption. Is the recombination process of a nonradiative kind by necessity?
nordmarj
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How do you make photoresist/photohardening paint?

I have been looking into making my own PCB's, but I noticed there is little information on making photo hardening paint. This is a critical component when etching the circuit, and I am very curious on the chemistry involved in making it. I…
fftk4323
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Cause of photoluminescence in CaV2O6

I had prepared the sample of Cav2O6 using solid-state reaction route. I had done XRD, SEM-EDS which all matched with the previous results. There was something strange when I did the PL analysis. I saw that most of the vanadates gave the…
Vikramjit Singh
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less toxic chemical laser chemistry

While most common lasers are electrically powered, there are also chemically powered lasers. These are high power systems, since for lower power systems electrically powered lasers (including optically pumped) are more practical. The chemistries I'm…
JanKanis
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