Interpreting IR/Raman Spectra Using Character Tables

  • Thread starter Thread starter greisen
  • Start date Start date
  • Tags Tags
    Spectra Symmetry
AI Thread Summary
To interpret IR/Raman data, understanding the symmetry of the molecular system is crucial. The designations "u" (ungerade) and "g" (gerade) relate to the symmetry of the wave functions, indicating whether the modes are symmetric or antisymmetric. To assign these modes to specific molecular motions such as stretching or bending, one should refer to the character table corresponding to the molecule's point group. Character tables provide detailed information on which vibrational modes are active in IR or Raman spectroscopy. These tables can often be found online or in specific chemistry textbooks, making them accessible for further analysis.
greisen
Messages
75
Reaction score
0
hi,

I am trying to interpret some data which have been calculated for IR/Raman but I don't know how to interpret them exactly. The schema says
mode \nu
1 b_u 82
1 a_g 216
2 b_g 239

I presume that the u/g are gerade/ungerade from the bonding/antibonding wave functions but how to assign these informations into stretch, bend etc. Is there a table where one can look these values up?

How to proceed any help appreciated. Thanks in advance.

 
Chemistry news on Phys.org
greisen said:
hi,

I am trying to interpret some data which have been calculated for IR/Raman but I don't know how to interpret them exactly. The schema says
mode \nu
1 b_u 82
1 a_g 216
2 b_g 239

I presume that the u/g are gerade/ungerade from the bonding/antibonding wave functions but how to assign these informations into stretch, bend etc. Is there a table where one can look these values up?

How to proceed any help appreciated. Thanks in advance.
You have to find out the symmetry of the system and then look at the character table for that point group. The meanings of a and b etc are all in the character table and will tell you which motions (bend, stretch) are raman active and which are not.
 
hi,

A character table - is it possible to find that online or does one have to consult a certain book?
 

Thread 'Humidity of a saturated NaCl solution with anticaking additive'

I want to test a humidity sensor with one or more saturated salt solutions. The table salt that I have on hand contains one of two anticaking agents, calcium silicate or sodium aluminosilicate. Will the presence of either of these additives (or iodine for that matter) significantly affect the equilibrium humidity? I searched and all the how-to-do-it guides did not address this question. One research paper I found reported that at 1.5% w/w calcium silicate increased the deliquescent point by...
View full post »

Thread 'Why does having 8 valence electrons make an element inert?'

I was introduced to the Octet Rule recently and make me wonder, why does 8 valence electrons or a full p orbital always make an element inert? What is so special with a full p orbital? Like take Calcium for an example, its outer orbital is filled but its only the s orbital thats filled so its still reactive not so much as the Alkaline metals but still pretty reactive. Can someone explain it to me? Thanks!!
View full post »

Thread 'Resists for etching Aluminium with NaOH'

I'm trying to find a cheap DIY method to etch holes of various shapes through 0.3mm Aluminium sheet using 5-10% Sodium Hydroxide. The idea is to apply a resist to the Aluminium then selectively ablate it off using a diode laser cutter and then dissolve away the Aluminium using Sodium Hydroxide. By cheap I mean resists costing say £20 in small quantities. The Internet has suggested various resists to try including... Enamel paint (only survived seconds in the NaOH!) Acrylic paint (only...
View full post »

Hot Threads

Recent Insights

Back
Top