11 votes

Why do glow-in-the-dark substances dim gradually?

There are two potential questions here: one is why is dimming a slow drawn-out process (incoherent, unlike a "switch"). The second question is why different stars may appear to lose their intensity at ...
Buck Thorn's user avatar
  • 21.4k
10 votes
Accepted

Lifetime components in phosphorescence decay

Phosphorescence should be at a longer wavelength than any fluorescence so carefully using a filter or grating should remove any fluorescence. Also measuring at different wavelengths will change ...
porphyrin's user avatar
  • 30.3k
8 votes
Accepted

Why are glow-in-the-dark things usually green?

The human eye is most sensitive in green wavelengths. Therefore, if one were to put the same amount of light energy into different wavelengths, the green portion of the spectrum would appear brightest,...
DrMoishe Pippik's user avatar
7 votes

Compounds with fluorescence and/or phosphorescence, what can do both?

An excited state has initially five possible fates, (1) internal conversion to a state of the same spin, (2) intersystem crossing to a state of different spin (e.g. singlet to triplet) (3) emission to ...
porphyrin's user avatar
  • 30.3k
7 votes
Accepted

Is it right to say that fluorescent lamps are actually fluorescent?

Fluorescent lamps do primarily work by fluorescence. According to this Wikipedia article: "The inner surface of the lamp is coated with a fluorescent (and often slightly phosphorescent) coating......
airhuff's user avatar
  • 17.4k
6 votes
Accepted

Why is a spin change favourable in intersystem crossing?

There are two things going on here. You have conflated with "forbidden" with unfavorable. In many systems, the first excited triplet is lower in energy than the first excited singlet. Hence, the order ...
levineds's user avatar
  • 3,070
5 votes

What chemical(s) in peanut butter cause it to glow under UV light?

Many natural oils from vegetable sources show intense fluorescence under UV. Olive oil glows brilliant red under UV. In the peanut butter case, my first guess was turmeric, the yellow spice, because ...
AChem's user avatar
  • 39.8k
4 votes
Accepted

Why do glow-in-the-dark substances dim gradually?

Source of light I imagine that the cause of the stars becoming dimmer is that some electrons are relaxing down before others. This statement could be interpreted in two different ways, one ...
Karsten's user avatar
  • 39.8k
4 votes
Accepted

Excited states and emission lifetimes

Yes, singlets fluoresce and triplets phosphoresce. So the singlet lifetime is the fluorescence lifetime and is the inverse of singlet excited state decay rate constant and similarly for ...
porphyrin's user avatar
  • 30.3k
3 votes

Excited states and emission lifetimes

Thanks @Achem and @porphyrin for your comments. I do not know if an Answer is the right format for this Comment but the comments do not allow enough character to develop my argument. I think we are ...
PAEP's user avatar
  • 1,051
3 votes

Fluorescence: what mechanism regulates the rate of discharge of energy?

The after-glow is called phosphorescence. Fluorescence stops immediately the moment light is turned off because the process is ultrafast! Phosphorescence on the other hand requires a change in the ...
AChem's user avatar
  • 39.8k
2 votes

Fluorescence: what mechanism regulates the rate of discharge of energy?

Although the previous answers correctly explain the different mechanisms of fluorescence and phosphorescence, they do not really touch upon why the light is not emitted all at once. Even in the very ...
Paul's user avatar
  • 2,396
2 votes
Accepted

Fluorescence: what mechanism regulates the rate of discharge of energy?

Phosphorescence is driven by the slow loss of energy from excited electron states Firstly, the phenomenon you describe is phosphorescence not fluorescence: they have different mechanisms. Fluorescence ...
matt_black's user avatar
  • 35.9k
2 votes
Accepted

If gaseous oxygen and dissolved oxygen (in water) have the same partial pressure, will they diffuse into solid materials at comparable rate?

If the air and water are in equilibrium, then che chemical potential of the oxygen in the air is equal to the chemical potential of the oxygen in the water. If either is placed in contact with your ...
Chet Miller's user avatar
  • 13.3k
2 votes

Excited states and emission lifetimes

Regarding porphyrin's response and PAEP's reservation about oxygen emission from an excited triplet to a ground triplet being labelled as fluorescence, the issue can be addressed by defining ...
AChem's user avatar
  • 39.8k
1 vote

How does this coin-and-strike-paper trick work (and is it safe)?

An opening comment from Wikipedia on phosphorus: The glow of phosphorus is caused by oxidation of the white (but not red) phosphorus — a process now called chemiluminescence. Now, my take, first ...
AJKOER's user avatar
  • 5,506
1 vote

Fluorescence: what mechanism regulates the rate of discharge of energy?

To answer why the energy is not emitted as a burst we have consider the chance of a photon being emitted. To match experimental data we have to assume that each event (photon emission) is randomly ...
porphyrin's user avatar
  • 30.3k

Only top scored, non community-wiki answers of a minimum length are eligible