Questions tagged [uv-vis-spectroscopy]

For questions that are related to the ultraviolet and visible spectrum of compounds, mostly due to electronic transitions between orbitals.

13 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
4
votes
0answers
40 views

Changing of UV-Vis peak absorption after heating Ni(en)2(NO2)2

(c) The trans-isomer of $\ce{Ni(en)2(NO2)2}$ D is red $(λ_\mathrm{max} = \pu{500 nm}).$ It can be heated to give a new trans-isomer E, which is violet $(λ_\mathrm{max} = \pu{560 nm}).$ Assume that, ...
4
votes
0answers
36 views

Nanoparticle Alloys (Gold-Silver) not forming

I have synthesised what I thought were gold-silver alloys at various different compositions. The UV/vis data showed that nanoparticles alloys with a majority of the composition made from gold had one ...
4
votes
0answers
119 views

Evaluating Franck-Condon factors

Franck-Condon overlap integrals are given by $\langle\psi^e_{v_e}|\psi^g_{v_g}\rangle$, where $\psi^e_{v_e}$ and $\psi^g_{v_g}$ are the vibrational functions for the $v^{th}$ vibrational states of the ...
2
votes
0answers
32 views

Are there any forbidden collisional electronic transitions?

There are spectroscopy selection rules marking some radiative electronic transitions as forbidden. For example, it is stated that single electron of H atom can not move from S2 to S1, or from P2 to S2 ...
2
votes
0answers
29 views

tolerable error, CASSCF simulation of UV/Vis spectrum

Please forgive my ignorance of experimental spectroscopy. I am a computational chemist, not an experimental one. My question is: what would be considered a tolerable or reasonable difference between ...
2
votes
0answers
116 views

Spectral database in the UV-Vis/NIR and IR regime

I'm searching for a bunch of spectra (some tens), preferably with intense bands in the Vis spectrum, to play around with (calculating chromaticity, etc.). They should range from 250 nm to 2500 nm (UV-...
1
vote
0answers
31 views

Why is the iron inter-system crossing non-negligible at high temperatures?

Inter-system crossing (ISC) is a radiationless process involving forbidden transitions between singlet and triplet state. These are more common with heavy atom molecules, so I understand that ISC is ...
1
vote
0answers
25 views

Why do carbonyl groups lower antibonding orbital energies of conjugated systems?

In the chapter on conjugation in Organic Chemistry by Clayden, Greeves, Warren and Wothers, there's a brief discussion of pigments with conjugated systems that includes the following paragraph (first ...
1
vote
0answers
27 views

Standard Solutions for UV-Spectrophotometry

Can one use a mixture of compounds when making a standard solution for UV-Spectrophotometry. For instance, one is attempting to find the casein concentration of milk using UV-spec and they have milk ...
1
vote
1answer
115 views

Equation for the equilibrium constant for the hydration of carbonyls using UV spectroscopy

I was looking through the literature when I found this source: https://pubs.rsc.org/En/content/articlepdf/1967/tf/tf9676302131 Which states that the equilibrium constant Khyd is: Khyd = $\frac{[...
0
votes
0answers
24 views

Why is absorption spectrum of beta-carotene different from Zeaxanthin?

Here are the molecular structures of beta-carotene and zeaxanthin These molecules only differ in the OH groups and the conjugated backbone length is exactly the same. I read that the absorption ...
0
votes
0answers
30 views

How do elemental halogens get their colour?

I learnt that in halogens the colour is due to transfer of electrons from HOMO to LUMO during excitation but I have trouble understanding what that means. Also I don't understand how iodine is ...
0
votes
0answers
25 views

Why absorption changes in schiff-base formation? Coenzyme PLP

Pyrodoxal-5-phosphate (PLP) in enzymes form schiff-base to lysine residue. This can be detected by the change in the absorption from 390 nm to 420 nm (free PLP to stiff-base bound PLP). I remember ...