Questions tagged [fluorescence]

This tag is for questions relating to "Fluorescence", an optical phenomenon in which the molecular absorption of energy in the form of photons triggers the emission of fluorescent photons with a longer wavelength.

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Thermally activated delayed fluorescence

In thermally activated delayed fluorescent (TADF) molecules, we consider 25% molecules in singlet first excited state and 75% in triplet, statistically, on electrical excitation after carrier ...
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Amplifying light with fluorophores

The fluorescein fluorescence spectrum shown below shows distinct excitation and emission peaks (with some overlap). If I were to "pre-charge" a fluorescein solution with a laser at ...
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Why are singlet and triplet states only relevant in organic semiconductors?

I found out that inorganic semiconductor lasers do not suffer from triplet accumulation as there is a strong mixing of the spin states but I still cannot see why that is? Is the reason a larger spin-...
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Why should dichroic mirrors be placed observing a certain orientation, and what happens otherwise?

I am getting very confused about the reason why dichroic mirrors should be placed observing a certain orientation. I read everywhere that you should place the mirror with the coated side facing the ...
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Will two spherical fluorescent particles have a lower fluorescence. When compared to one spherical fluorescent particle with the same volume?

So image you have two groups one group consist out of 1 fluorescent particle and the other group consist out of multiple particles. However, the volume of the particles combined is the same for both ...
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How would you remotely detect interaction of a beam of 1 GeV protons with an aluminum sheet?

The inelastic interaction with an electron of the aluminum atom would knock them out of the atom, and would give rise to emission lines characteristic of aluminum when a free electron filled the ...
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Do atoms emit and absorb photons at the same wavelengths?

I know that atoms absorb photons, which promotes electrons to higher energy levels. Then upon de-excitation a photon is released. Is it true that the lines for absorption and emission spectrums are ...
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Why a mode-locked reduce the integration time in microscopy?

Why a mode-locked (laser) reduce the "integration time" in two-photon fluorescence microscopy?
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Strange Interference under monochromatic light

I'm coming to you with a strange physical/optical phenomenon I noticed today for which I'm looking for an explanation. I can't seem to find references to this, and it was pretty surprising to see for ...
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Dependency of molecular spontaneous emission on the refractive index

I am familiar with the following equation for the spontaneous emission rate, $$ \Gamma_{em}(\omega_{if}) = \frac{\omega_{if}^3}{3\pi\varepsilon_0\hbar c^3} |\mu_{if}|^2\tag{1} $$ where $\omega_{if}$ ...
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Spectrum of laser light absorbed and re-emitted by a white object

If I shine a red laser onto a white surface, I assume that: some of the red light will be nearly instantly reflected, some will be absorbed and converted into phonons and some will be absorbed and re-...
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Would UV-induced-visible-fluorescence indicate the presence of vividly reflecting UV-invisible-light?

Some people take amazing photos by using UV-induced-visible-fluorescence(UVIVF). In my understanding, we see in these photos VISIBLE light induced by UV. https://www.nationalgeographic.com/photography/...
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If not fluorescence, what is the process of emission and absorption of white light by everyday objects?

An electron in an atom is excited by a photon and moves to a higher energy state. The electron then relaxes and transitions to a lower energy state emitting a photon of longer wavelength than that of ...
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How do Fluorescent molecules emit light in a different wavelength than the one needed to excite them?

if it took a very certain amount of energy to excite an atom, how come when it de-excites it emits a photon of lower energy? I know that's what scintillators do, I Just want to know the microscopic ...
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Looking for ideal calibration standards for UV / visible fluorescence

I am attempting to measure the fluorescence timing distribution (how much light is emitted over time from initial excitation) of a substance and I would like to use a solid calibrated sample (some ...
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Reconciling two descriptions of fluorescence

I am currently studying the textbook Infrared and Raman Spectroscopy: Principles and Spectral Interpretation, second edition, by Peter J. Larkin. Section 9. Selecting the Raman Excitation Wavelength, ...
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Is there any equivalence or "fluorescence" in acoustics?

Fluorescent materials convert some visible or invisible electromagnetic radiations from a certain range of frequencies to another one, usually from higher to lower frequencies, rarely, the other way ...
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Is the Crookes tube with Maltese cross (cathode rays) safe in terms of produced X rays at 5-10kV DC (1–10mA) during, say, 15 seconds of work?

I would like to get some information on the operational safety of this equipment. How much, approximately (just the order of magnitude) does the school Crookes tube with the Maltese cross, used to ...
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Electronic-vibrational-rotational Transition

I'm trying to simulate the fluorescent spectrum for the first time and run into several problems. The dipole matrix element for a transition between 2 different electronic states is as follow: $$\...
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If a fluorescent atom absorbs UV and emits visible light, then how is energy conserved?

Light has a lower frequency than UV, so unless energy is also released in other forms, how can energy be conserved? What other forms is energy released as for fluorescence?
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What is the difference between lasers and fluorescense?

In both cases I see few low energetic levels, few upper energetic levels, some no-emission transitions between upper levels and main downwards transition called either fluorescence or laser. Here is ...
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Why fluorescence lifetime in laser crystals decreases while dopant concentrations increases?

I noticed, that is laser crystals the low levels of doping are used and that if higher levels did, the lifetime of excited level will be shorter. Why? The atoms of dopant are the same. Why do they ...
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Can phosphors exhibit stimulated emission?

I read that phosphorescence is caused because of the presence of "forbidden" energy states. This causes the photon that is absorbed to not be immediately emitted like fluorescence but emitted after a ...
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What causes a light bulb to fluoresce?

When an incandescent light bulb or fluorescent light bulb is pumped up with energy from the power grid, presumably light is subsequently emitted via transitions from the molecular excited state to it'...
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Can (diatomic)fluorine gas discharge tubes be used as a UV light source?

Looking at the emission spectrum of fluorine there are 2 sharp peaks in teh far ultraviolet band. I haven't been able to find any direct images/articles about fluorine gas discharge tubes being used ...
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Optimal paint for UV fluorescence?

If we assume that a light source with 365 nm is the optimal source for how strongly we perceive UV light when it hits a UV fluorescent surface, what would be the optimal colour to paint such a surface ...
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Is it possible to make a fluorescent material that only glows in response to a specific UV wavelength?

There are any number of fluorescent materials that glow when exposed to UV light. But what if I wanted such a material that only glows in response to very specific wavelengths, emitting no visible ...
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fluorescence wavelength limit

My understanding is that fluorescence occurs when light has sufficient energy to excite an electron, which then emits a different photon (always with a larger wavelength) and releases the energy it ...
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What is the nature of vibrational relaxation in fluorescence?

Electrons in fluorescent substances get excited from the ground state($S_o$) to the first excited state($S_1$) or higher excited states in case of upconversion. Depending on the statistical ...
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Timescales of plasma recombination and fluorescence?

I am currently working on a very simple model for the radiation from electric arcs. As both fluorescence (internal electronic transition) and plasma recombination occur, I would like to compare the ...
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Photon Spin in Fluorescence and Phosphorescence

I think i still lack basic understanding of how absorption and emission of light actually works. Like fluorescence is the radiative transition from an excited singlet state to the ground (singlet) ...
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Requirements for a fluorescent medium to provide optical gain

I have seen fluorescent material such as Rhodamine 6G being used as a gain medium in dye lasers. My understanding is that by pumping the medium with energy, we can make stimulated emission happen ...
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3 answers
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Why is there not a solid state fluorescent lamp?

Is it possible to coat a solid piece of metal with fluorescent powder (such as in a tube), and get this to emit light in a strong electric field?
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DNA - optical response and fluorescence

I am curious about the state of affairs with the DNA fluorescence. I know that there was some initiative in physics community in 1980's and 1990's, but some authors question even whether DNA molecules ...
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If blackbody radiation at 6000K peaks in the optical, why aren't fluorescent bulbs at 6000K?

We know, via Wien's law, that a body at 6000K emits an electromagnetic wave at the peak wavelength in the visible spectrum. How come say the fluorescent tubes which also emit the EM waves that we can ...
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Fluorescence photons per event

When a high-energy photon hits a material that fluoresces, what formula can you use to determine how many photons will radiate out as the material de-excites? I would like the most general formula ...
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Cannot observe Raman signal from Styrofoam

I am trying to build a low cost Raman spectrometer. I am using a refurbished B&WTek spectrometer that I purchased from eBay. I calibrated the unit myself and found to be very sensitive and ...
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What are some mechanisms that can lead to unexpected/anomalous spectral lines

I am studying fluorescent spectroscopy (laser-induced fluorescence spectroscopy specifically). In a particular atomic spectrum, there are some unexpected lines not associated with any known ...
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Can a plasma ball light up minerals that fluoresce?

I want to know if I could use a plasma ball to light up a UV poster that are typically activated by blacklights. option 1: using light from the globe According to my research it seems that the light ...
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1 answer
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Two-photon absorption fluorescence of air

I'm wondering if there are any major constituents of air which are capable of undergoing two-photon absorption and ultimately fluorescing in the visible spectrum. The original wavelengths of the ...
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1 answer
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Fluorescence or phosphoresence?

Is there any theoretical way to know if a material emits a fluorescent light or a phosphorescent one? Is there any relationship between this process and the singlet-triplet energy splitting $\Delta E =...
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1 answer
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Raman Scattering vs. Fluorescence (1-photon / 2-photon process) [duplicate]

I have a question considering the difference between Raman Scattering and fluorescence. I know that Raman Scataring is a non-resonant process, while fluorescence is resonant, that Raman scattering ...
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2 votes
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Why is a white LED color spectrum more continuous than CFL spectra?

As far as I understand, white LEDs and CFLs both use phosphor mixtures to convert part of their primary emission spectrum to longer wavelengths. What puzzles me is the difference in the resulting ...
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"Fundamentalrelation of Resonance Fluorescence" - How can it be?

In my quantum optics lecture, I was given the formula: $$ \vec{d}_{eg} \hat{\vec{E}}^{(+)} = \frac{i \kappa \hbar}{2} | g \rangle \langle e | $$ Here, $\vec{d}_{eg} = \langle e | \hat{\vec{d}} | g \...
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Is it valid to compare experimental data and theoretical data like this? Does the vertical axis of the graphs have to correspond?

The plotted curve is the experimental value of the SPD curve. Though it doesn't look "spikey" as it should, stacking the image on top seems to explain that the data is infact correct, but that more ...
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Can heat cause flourescence or phosphorescence at STP?

I am aware that chemical reactions may cause fluorescence. Most fluorescence results from adding light and then watching the captured light re-emit. Is there any that doesn't require adding light, ...
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30 votes
4 answers
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What are these alternating bright and dark rings in fluorescent lamp?

I'm quite surprised by these regularly spaced rings of alternating brightness in a fluorescent tube. These are also moving along the tube and only appear when the voltage is low. What are these and ...
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Limits single fluorophore, simultaneous absorption and emission

So I've been trying to find out what the limitations are for single fluorophores. What I know is that a fluorophore is excited by a photon in too a higher excited state, it then relaxes and later ...
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Collisional quenching in fluorescence

I am studying collisional quenching phenomenon in fluorescent measuring and I am focusing on Stern - Volmer relationship. I can't understand why the ratio of the intensities of fluorescence is equal ...
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2 votes
1 answer
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Can we have a three-level system with mixed parity and transition dipole moments in different directions?

I would like to know if there are molecules described by a three-level system with mixed parity and transition dipole moments in different directions. By mixed parity I mean all three transitions can ...
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