Difference between revisions of "HCl Vibrational-Rotational Spectroscopy"

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:so you can solve for B<sub>e</sub>...
 
:so you can solve for B<sub>e</sub>...
  
:and Be  
+
:and Be = [[File:Screen Shot 2020-03-26 at 9.36.14 AM.png|200px]]
 
 
[[File:Screen Shot 2020-03-26 at 9.36.14 AM.png|400px]]
 
  
 
::https://en.wikipedia.org/wiki/Isotopes_of_chlorine
 
::https://en.wikipedia.org/wiki/Isotopes_of_chlorine

Revision as of 14:36, 26 March 2020

Adapted from Experiment #38 (Shoemaker, Garland, Nibler, 1989)

See Chapter 8 (Engel), more will be presented in lecture...

Sample Preparation

a) Pull the HCl (g) off the headspace of a bottle of concentrated HCl using a 60 mL syringe.
b) deliver the HCl (g) to the gas-sampling IR cell.

IR Gas-Phase Data Collection

a) Collect data using the highest resolution.
b) average 32 scans (both background and sample)
c) Save-As...
(A complete set of data can be found here.)

Spectral Analysis

a) load IR data into Igor or Excel.
b) Use the cursor tool to tabulate the H35Cl and H37Cl data into separate columns,
c) Assign an "m-value" to each transition (note the 'm=0' forbidden transition) with the help of the following graphic (click to make bigger).
Screen Shot 2020-03-26 at 8.48.29 AM.png

Data Analysis

Okay, so you should now have a table, probably in Excel but if you know how to do it in Igor then great (Igor does not offer any advantages here) with heading like this:

m-value H35Cl H37Cl
-12 XXXX YYYY
-11 XXXX YYYY
-10 XXXX YYYY
-9 XXXX YYYY
... ... ...
+1 XXXX YYYY
+12 XXXX YYYY
+13 XXXX YYYY
a) Make a plot, m-value verses freq (in 1/cm) for H35Cl data; this will NOT be a straight line but a polynomial curve.
b) fit a second order polynomial to this data... ie y= ax2 + bx +c, and note the values for a, b, and c in your notes (lab notebook preferred).
c) During our last lab period you were given a Shoemaker, et al. handout (???) that discussed this lab activity. Eq. 9 was:
ṽ = ṽo + (2Be - 2 αe) m - αe m2, which has the form y = c + bx + ax2

a = αe
b = 2Be - 2 αe
so you can solve for Be...
and Be = Screen Shot 2020-03-26 at 9.36.14 AM.png
https://en.wikipedia.org/wiki/Isotopes_of_chlorine
atomic masses in amu
Reduced mass, "mu" = (m1*m2)/(m1+m2)
1H 1.007825 amu (99.9885%)
35Cl 34.968853 amu (75.78%)
37Cl 36.965903 amu (24.22%)
conversion factor: 1.66054e-27 kg/amu

4) Plot "m" (x) vs the frequency (y) and fit to a second order polynomial.

5) The second order polynomial will take the form of equation 9 from (Exp 38, Shoemaker), hence you can determine alphae, and then of Be.

6) Using equation 5 and 3, then solve for "r" the average internuclear separation.