Compiled presentations MOS

1. Molecular Spectroscopy By: Leland Breedlove, Andrew Hartford, Roman Hodson , and Kandyss Najjar

2. Roman hodson Theory and Introduction

3. FTIR Spectroscopy University of California at Davis Chemistry Department. FTIR Block Diagram [Image ] Retrieved April 14, 2015 . Time domain data to frequency domain data Need fast time scales Light is split and reflected off a motorized mirror Fourier transforms interferogram into a spectrum

4. Rotational/Vibrational Energy Levels Vibrational Energy: Rotational Energy: G(v ) = (v + ½) ν e F(J) = BJ(J+1) MIT. (n.d.). Principles of Molecular Spectroscopy . Retrieved March 23, 2015, from http://web.mit.edu/ 5.33/www/ lec /spec4.pdf. Rotational levels nested between vibrational levels J is rotational quantum number, v is vibrational quantum number Total energy is the sum of the two Selection rules

5. P and R Branches UC Davis. (n.d.). Rovibrational Spectroscopy. Retrieved April 14, 2015, from http://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Rotational_Spectroscopy/ Rovibrational_Spectroscopy Higher rotational levels can be populated at room temperature ΔJ = +1, rotational transition added to vibrational energy (R) ΔJ = -1, low wavenumber side of branch (P)

6. Harmonic Oscillator University of Liverpool. (n.d.). Vibrational Spectroscopy . Retrieved March 13, 2015, from http://osxs.ch.liv.ac.uk/java/spectrovibcd1-CE-final.html. All energy level spacing is equal (h ν ) Equilibrium bond length is the same at all energy levels Forbids vibrational transitions of Δ v ≠ ± 1 Does not account for bond dissociation/repulsion

7. Anharmonic Oscillator University of Liverpool. (n.d.). Vibrational Spectroscopy . Retrieved March 13, 2015, from http://osxs.ch.liv.ac.uk/java/spectrovibcd1-CE-final.html. Shows equilibrium bond length changes The spacing between energy levels decreases at higher quantum numbers Models bond dissociation/repulsion Allows for overtone transitions: Δ v > ±1

8. Absorption Δ E = h ν A = ε lc A = -log(I/I o ) Use range of wavelengths Provides information about the excited state energy levels   UC Davis. (n.d.). Infrared: Theory. Retrieved April 14, 2015, from http://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared%3A_Theory

9. Emission Microscopy Resource Center. Jablonski Energy Diagram; Excitation and Emission Spectrum [Image ] Retrieved April 14, 2015 . Δ E = h ν Use single wavelength to excite to a particular excited state Electrons relax back to various vibrational levels in the ground state Provides information concerning the ground state

10. Franck-Condon Principle UC Davis. (n.d.). Selection Rules and Transition Moment Integral . Retrieved April 14, 2015, from http://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Fundamentals/ Selection_rules_and_transition_moment_integral Born-Oppenheimer approximation Demonstrates vibronic transitions The wavefunctions in ground and excited state must overlap Peak intensity is proportional to amount of overlap

11. Analysis of carbon monoxide through its rovibrational spectrum Andrew Hartford

12. Experimental method Evacuated and collected background spectrum of gas sample cell using FTIR spectrophotometer Filled sample cell with 100 mmHg CO, collected spectra at resolutions of 4, 2, 1, 0.5, 0.25 cm-1 Stored gas sample in desiccator when not in use

13. Results Fundamental Absorbance Spectrum (CO) between 1950-2275 cm -1

14. First overtone (CO) between 4100-4400 cm -1

15. Wavelength vs. m values (Fundamental spectrum)

16. Wavelength vs. m values (First overtone spectrum)

17. Constatnts Fundamental (cm -1 ) First Overtone (cm -1 ) 2142.9 4259.6   Equilibrium Frequency (cm -1 ) α e (cm -1 ) B e (cm -1 ) D e (cm -1 ) χ e (cm -1 ) Experimental Value 2168.8 0.0143 1.90 1.5 x 10 -5 0.00599 Literature Value 19 2169.8 0.0175 1.9313 6.2 x 10 -6 0.00612 Percent error 0.0461% 18.3% 1.62% 142% 2.12%

18. Molecular constants   Moment of Inertia (kg m 2 ) Equilibrium bond (Å) Force Constant (N/m) Experimental Value 1.47 x 10 -46 1.14 1903 Literature Value 19 1.4490 x 10 -46 1.1281 1902 Percent error 1.45% 1.05% 0.0526%

19. Global Warming Potentials of Greenhouse Gases Kandyss Najjar http:// commons.wikimedia.org /wiki/ File:Earth's_greenhouse_effect _(US_EPA,_2012). png

20. Brief Theory GWP - heat trapped by greenhouse gases when exposed to IR radiation emitted from the Earth quantity , strength, and location of IR absorption bands Researchers and political activists – effects on climate change Radiation forcing capacity – sum of IR spectrum and emission of Earth blackbody radiation Equivalent to the GWP relative to gas atmospheric lifetime RFC can be determined relative to a reference gas Normally CO 2 **Elrod, M. J. J. Chem. Ed .  1999 ,   76 , 1702-05.

21. Brief Theory (Cont.) The radiation forcing capacity is given by Equation 1 RF A – radiation forcing capacity per 1 kg increase of sample A (t) – time decay of a pulse of sample RF R and R(t) – same, but for reference Equation 2 – determine GWP in terms of mass instead of molecule τ – atmospheric lifetime (years) MW – molecular mass (g/ mol ) Equation 1 Equation 2 **Elrod, M. J. J. Chem. Ed .  1999 ,   76 , 1702-05.

22. Experimental NaCl cell evacuated as per Week 1’s procedure Using OMNIC – background spectrum Range: 495 – 1600 cm -1 Resolution: 1 cm -1 Filled g as cell with: CH 4 – 60.0 Torr N 2 O – 60.1 Torr IR spectra taken for both gases Range: 495 – 1600 cm -1 Resolution: 1 cm - 1 http:// www.specac.com /assets/products/49903cada5f6c.jpg

23. Expected Results Nitrous Oxide Fundamental: ~600 cm -1 First Overtone: ~1300 cm -1 Methane First Overtone : ~ 1200 cm -1 to ~ 1400 cm -1 N 2 O CH 4 Molecular Spectroscopy. University of Texas at Austin - Chemistry Department.  Canvas.utexas.edu  ( accessed April 26, 2015) .

24. Experimental Results IR spectra obtained w ere very similar to the expected spectra Nitrous Oxide Fundamental: ~600 cm -1 1 st Overtone: ~1300 cm - 1 Methane 1 st Overtone: ~ 1200 cm -1 to ~ 1400 cm - 1

25. Calculating Global Warming Potential (GWP) Converted IR spectra to CSV files Using Excel, constructed table 505 – 1495 cm -1 , in increments of 10 cm -1 =lookup function to add corresponding IR absorbance data Inserted table into provided “Global Warming Potential Model” spreadsheet Path length: 10 cm L ifetime, formula weight, and gas pressure in cell** N 2 O – 120 years, 44.01 g/ mol , 60.1 Torr CH 4 – 15 years, 16.04 g/ mol , 60.0 Torr Time Horizons: 20, 100, and 500 years **Elrod, M. J. J. Chem. Ed .  1999 ,   76 , 1702 -05.

26. Results GHG Lifetime (Years )** Time Horizon (Years) Calculated GWP Literature GWP** Percent Difference (%) N 2 O 120 20 73.3 93 21.1 100 69.3 88 21.3 500 60.9 77 20.9 CH 4 15 20 33.3 37 10.0 100 11.6 13 10.9 500 5.9 6 2.46 **Elrod , M. J. J. Chem. Ed .  1999 ,   76 , 1702-05 .

27. Short Summary IR spectra obtained match expected spectra Nitrous Oxide Fundamental: ~600 cm -1 1 st Overtone: ~1300 cm -1 Methane 1 st Overtone: ~ 1200 cm -1 to ~ 1400 cm - 1 N 2 O is a more effective greenhouse gas Larger atmospheric lifetime Larger GWP  more efficient at trapping heat within atmosphere

28. Leland Breedlove Absorbance And Emission Of Iodine Gas

29. Experimental I 2 absorption spectra Halogen lamp Detector inline with beam I 2 emission spectra Argon LASER Detector arranged 90° to laser Filter used to maximize area of interest

30. Absorption

31. I 2 Absorption Bandhead Energy versus v’ + ½

32. Emission

33. I 2 Emission Bandhead Energy vs v” + ½

34. B-State and X-State Constants Spectroscopic constants Experimental values (cm -1 ) Literature Values 12 (cm -1 ) Percent Error (%) G”(0) 138.15 107.11 29.0 v” e 224.93 214.53 4.85 v e x” e 2.14 0.6130 249 v e y” e -0.5177 0.0754 73303.88 D” o 11731.229 12440.2 5.70 E(I*) 7927.4 7602.98 4.27 Spectroscopic constants Experimental values (cm -1 ) Literature Values 12 (cm -1 ) Percent Error (%) G”(0) 138.15 107.11 29.0 v” e 224.93 214.53 4.85 v e x” e 2.14 0.6130 249 v e y” e -0.5177 0.0754 73303.88 D” o 11731.229 12440.2 5.70 E(I*) 7927.4 7602.98 4.27

35. B-State Morse Potentials Spectroscopic constants Experimental Values Literature Values 12 Percent Error (%) D ’ e 3968.578 cm -1 4381.2 cm -1 9.42 R’ e Used Lit. Value 3.0267 Å n/a T e 15828.15 cm -1 15769.1 cm -1 0.374 v’ e 84.603 cm -1 125.67 cm -1 32.7

36. Morse Potential plots FCintensity

37. Discussion Morse potentials show longer eq. bond length for X-state than B-state ----Not good Data shows less transitions than literature predicts largest Franck-Condon factor from the emission spectrum at v” = 5, at 544 nm The results from our calculations are more reliable than FCIntensity values equilibrium bond length of the X-State is less than that of the B- State

38. Questions?