CHEM 3493 - Experiment # 3 -Molecular theories

Measurements of rovibrational spectra,  modeling of energy levels and the state population distributions
 

LIST:

1. Notebook: pre-lab report, all results from lab notebook, all work done in the notebook written in lab notebook

BEFORE THE EXPERIMENT: Read EXPERIMENT 37 and related material from the texbook. In this experiment we examine the so called nuclear rotation and vibration of the assigned molecules. You may need to prepare or make the molecules or compounds (see handouts or texbook). OBSERVE ALL SAFETY RULES IN THE LAB!  You will also read and become familiar with the FTIR instrument and the basic physico -chemical principles on which it operates (see textbooks and manuals. . 

2. Mathematica (or similar ): all calculations and uncertainty calculations

* You will write all needed expressions - see textbook and this page to find what you need to calculate and model in Mathematica - and do the calculations before submission of results to this webpage. In the Mathematica program assign the values to the standard physical constants first (example: h, c, etc). Make sure that all input values are in real number format ("with decimal point"). USE THE CORRECT and CONSISTENT SET of UNITS The dimensional equations could be calculated the same way as numerical-but be careful.

Use Mathematica for the calculation of the propagation of uncertainties expressions. You can practice the model calculations and uncertainty calculation using available literature data Use the Mathematica FTIR example file from this web site to see how to do the modeling and calculations (in class).

3.This web submission

Fill in the blank fields below with your measured data, results of (Mathematica) modeling, simulations  and calculations. After you have re-checked that all of your values are entered correctly, print out a hard copy of confirmation page for your record to be submitted with your pre-lab and the copies of lab-notebook sheets. You are allowed to submit data more than once-if you make entry error; so make sure your last entries are correct.   Then click on the submit button.

 

4. Report in .doc format (abstract, intro, results&discussion, conclusions, references)

You can use the calculations from Mathematica and cut-paste copy into report.

*You can attach/submitt by e-mail with CHEM3493-experiment#-YOUR NAME all on that list, except the copies from notebook. Also ,when needed, computer generated work (acquired data in files, images, including all instrument-software, LabView, Mathematica, Excel files, Gaussian03or PeakFit files etc. ).

 

Additional postexperiment work (experiment # 6) will include QM software based (Gaussian) modeling of the electronic potential energy distribution as a function of molecular nuclear geometry. You will read and learn about the state to state transition models and the electromagnetic and molecular physical objects involved. You will read and learn about the state and state - to -state assignments. You should be able to extract information about the molecular vibrational parameters from the measured energies and population intensities using simple mathematical programs, Use Gaussian 03 example file for the additional report on the electronic potential surface.


Name:
Group:
Instrument (s) used
Chemicals used
TA:

Pre-lab information:

What is the common name for the model used for the vibrational energy estimates
What is the common name for the model used for rotational energy estimates ?
What is the lowest vibrational energy?
What is the lowest rotational energy?
A molecule is in the rotational state J=2, what are the possible rotational states if the system is excited to the first vibrational state?

What is the name of the most simple electronic potential model ?
Are you preparing your own sample of HCl (yes/no)?
What program do you use for the identification of transition energies?

(Excel. instrument, Mathematica..)

What is your estimate of the instrument resolution?

Can you distinguish between the 35 and 37Cl?

Results and determination of molecular constants for HCl and

DCl:

A) Measured values and standard uncertainty (prop. of uncertainty - confidence intervals)

 HCl : B constant  +_  units -here, NOT in the field
 DCl : B constant +_ units
 HCl : a constant +_ units
 DCl : a constant +_ units
 HCl : D constant +_ units
 DCl : D constant +_ units
 HCl : 0-0 vibrat. transition energy +_ units
 DCl : 0-0 vibrat. transition energy +_ units
 HCl :  nx transition energy +_ units
 DCl : nx transition energy +_ units
HCl: k- H.O. constant: +_ units
DCl: k- H.O. constant: +_ units
HCl: I momentum constant: +_ units
DCl: I momentum constant: +_  units
HCl: re constant: +_  units
DCl: re   constant: +_  units

B-Reported (literature, Herzberg) values and % discrepancy:

100* (measured-true)/true

 HCl : B constant   %    units
 DCl : B constant %
 HCl : a constant %   units
 DCl : a constant %_
 HCl : D constant %  units
 DCl : D constant %
 HCl : 0-0 vibrat. transition energy %  units
 DCl : 0-0 vibrat. transition energy %  units
 HCl :  n x transition energy %  units
 DCl : n x transition energy %
HCl: k- H.O. constant: +_  units
DCl: k- H.O. constant: +_
HCl: I momentum constant: +_  units
DCl: I momentum. constant: +_
HCl: re   constant: +_  units
DCl: re constant: +_

****For the following : If you are submitting data in the Mathematica .nb file

you do not need to fill in all the data. You must assign the J quantum numbers and N values to the first 3 lines in P and R progressions.

FTIR spectrum of HCl - peak positions: (copy from your data file)
 
(signed ) # m (for fit)
 Jlow #  P, R (or Q) Energy of transition (cm-1) Transmittance Absorbance (calculated) Population (calculated)
1
2
3
-1
-2
-3

 

 

FTIR spectrum of DCl - peak positions: (copy from your data file)
 
(signed ) # m (for fit)
 Jlow #  P, R (or Q) Energy of transition (cm-1) Transmittance Absorbance (calculated) Population (calculated)
1
2
3
-1
-2
-3

 

Masses:
 

1H
D (2H)
 35 Cl
37 Cl


Print and save a hard copy of this and save the conformation page, for your records.


 
 


 
 



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Louisiana State University, Department of Chemistry.
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