The flames of Romance The flames of Romance Candlelight and Chemistry Molecular spectroscopy and reaction dynamics Arnar Hafliðason April 10 th 2015

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<ul><li> Slide 1 </li> <li> The flames of Romance The flames of Romance Candlelight and Chemistry Molecular spectroscopy and reaction dynamics Arnar Hafliason April 10 th 2015 </li> <li> Slide 2 </li> <li> The beauty of science Lets begin with Richard Feynman The story about the flower and his artist friend </li> <li> Slide 3 </li> <li> You, light up my life What is a candle made of..? What is needed for it to burn..? What is, to burn..? Why is fire, yellow.. Why is fire, blue? Lets gaze into the flames and see whats cookin? </li> <li> Slide 4 </li> <li> What is candle made of? Paraffin wax C 31 H 64 Or actually a mixture of long hydro- carbon molecules, i.e. C n H 2n+2, ranging from n=25-40. Paraffin wax is a white or colorless soft solid derivable from petroleum Candle wick, a braided cotton that holds the flame of a candle </li> <li> Slide 5 </li> <li> What is needed for it to burn? Prerequisite is OXYGEN Oxygen around is usually enough, though you might want to add more oxygen to spice things up You need the spark for the chemistry to happen The process needs to be exothermic to sustain itself The rate of the chemical reactions needs to be fast enough to keep the process going Some source of hydrocarbons (gas, wax) for the oxygen to react with </li> <li> Slide 6 </li> <li> What is, to burn? Exothermic Reaction Energy </li> <li> Slide 7 </li> <li> Energy from exothermic reaction Divided into 2 main groups 1.Kinetic Energy (Vibration, Rotation, translation) E kin = nk B T (Increase in temperature =&gt; more energy) HEAT 2.Radiation Energy (emission following e - transfer) E = h = h(c/ (shorter wavelength =&gt; more energy) LIGHT </li> <li> Slide 8 </li> <li> What is, to burn? Exothermic Reaction ????? Could this explain the different colors in the fire?? Energy Reactive radicals are formed </li> <li> Slide 9 </li> <li> Why is fire, yellow.. Why is fire, blue? it depends on what youre burning and what the heat is when its burning </li> <li> Slide 10 </li> <li> 1)Just gas, no extra oxygen (candle) 2)Gas, and little bit of oxygen 3)Gas, and oxygen 4) Gas, and a lot of oxygen Lets connect a gas- burner: propane gas cylinder and oxygen cylinder </li> <li> Slide 11 </li> <li> Heat from steps 1) 4) estimated around 1000 K 3000 K. 1)Yellow because of incomplete com- bustion caused by lack of oxygen. What we see as yellow/white is soot (C n (s)) that is glowing Less combustion Less heat less blue Propane/Oxygen 4)Blue because of complete combustion caused by abundance of oxygen. Notice the flame is almost clear above the blue inner core More combustion More heat more blue </li> <li> Slide 12 </li> <li> Gaze into the flames and see whats cookin Monochromator separates light into wavelengths </li> <li> Slide 13 </li> <li> Experimental setup /Mono- chromator / gas burner /PMT/inlet slit </li> <li> Slide 14 </li> <li> Diffraction grating Source about 4 cm from slit Opening is 5x5 mm Slit settings: 10, 30 and 50 m </li> <li> Slide 15 </li> <li> Measured emission spectra </li> <li> Slide 16 </li> <li> Radicals and radiation C 2 and OH radicals Emission at 516 nm, the C 2 radical is in excited electronic state, it relaxes to a lower energy state, d 3 a 3 , giving of radiation equal to that energy-difference Emission at 308.6 nm, the OH radical is in excited state and is relaxed to the ground state, A 2 + X 2 , giving of radiation equal to that energy-difference </li> <li> Slide 17 </li> <li> Radicals and radiation CH radicals Emission at 430.7 nm, the CH radical is in excited electronic state and relaxes to the ground state, A 2 X 2 , giving of radiation equal to that energy-difference Emission at 389.1 nm, transition: B 2 - X 2 Emission at 314.7 nm, transition: C 2 + X 2 </li> <li> Slide 18 </li> <li> A = 430.7 nm What do I mean by energy- difference? h = 430.7 nm h: Planck constant c: speed of light constant : wavelength of light CH Potential curves for the CH molecule B = 389.1 nm C = 314.7 nm = 389.1 nm = 314.7 nm </li> <li> Slide 19 </li> <li> Radicals and radiation Emission observed is found at: 314.7, 389.1 and 430.7 nm for CH, 308.6 for OH and 516 nm for C 2 Human color vision </li> <li> Slide 20 </li> <li> Measured emission spectra </li> <li> Slide 21 </li> <li> Vibrational and rotational structure v 0 1 2 3 4 0 1 2 3 v A2A2 X2X2 Measurement </li> <li> Slide 22 </li> <li> Location of vibrational bands nm Measured Calculated Total v=3 v=3 v=2 v=2 v=0 v=0 v=1 v=1 </li> <li> Slide 23 </li> <li> Rotational structure for v=0 v=0 transition. 4 6 8 10 14 J=20 Measurement </li> <li> Slide 24 </li> <li> Spectral simulation at T=3000K Simulation with PGOPHER Measurement Simulation Lambda doubling e-e- </li> <li> Slide 25 </li> <li> Simulation on A 2 X 2 for v=0 v=0 B=14.17 A=29.75 D=0.00142 B=14.56 A=-1.1 D=0.00152 B=14.19 A=27.95 D=0.00148 B=14.57 A=-1.1 D=0.00146 CalculatedConstants from NIST Minimal adjustment of constants from NIST (National Institute of Standards and Technology). B: Rotational constant D: Centrifugal distortion A: Spin-orbit coupling cm -1 X2X2 A2A2 </li> <li> Slide 26 </li> <li> Few measurements under different circumstances 1.Different quantity of oxygen burned with propane gas, 5 different settings 2.6 different height settings of the slit from the source of the flame </li> <li> Slide 27 </li> <li> 3 cm 3 mm Slit </li> <li> Slide 28 </li> <li> 2x O 2 1900 K 4x O 2 3000 K 3x O 2 2200 K Difference in rotational distribution. More heat is observed with increase in use of oxygen. Simulations: </li> <li> Slide 29 </li> <li> Comparing population distribution. Experiment vs. Boltzmann distribution J=7 J=6 T = 2200 KJ max = 6.74 </li> <li> Slide 30 </li> <li> 3x O 2 0 mm 50 mm 15 mm </li> <li> Slide 31 </li> <li> 3x O 2 0 mm 50 mm 15 mm </li> <li> Slide 32 </li> <li> Slide 33 </li> <li> Thank you all for coming </li> <li> Slide 34 </li> <li> Some equations Boltzmann distribution Hnl-London factors </li> <li> Slide 35 </li> <li> Frank-Condon factors. Can calculate transition probability between vibrational states v and v v v 0 0 1 1 2 2 3 3 4 4 </li> <li> Slide 36 </li> <li> Voltage and slit Intensity for different settings was measured Slit settings: 10, 30 and 50 m Voltage settings: 900 and 1000 V </li> <li> Slide 37 </li> <li> 156 cm-1 </li> <li> Slide 38 </li> </ul>