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Vernier Flash

Photolysis

Spectrometer

(order code: VSP-FP)

Educational Flash Photolysis Spectrometer

Reference Manual

(version: 12/14/2015)

Summary of Contents for VSP-FP

Page 1: ...Ultrafast Systems LLC Vernier Software Technology Vernier Flash Photolysis Spectrometer order code VSP FP Educational Flash Photolysis Spectrometer Reference Manual version 12 14 2015...

Page 2: ...15 5 1 Stoichiometry 15 5 2 Reaction Rate 15 5 3 The Rate Expression and the Rate Constant 16 5 4 Order of Reaction 17 5 5 The Experimental Approach 18 5 6 The Relationships Between Rate Constant Half...

Page 3: ...ure 12 Ground state absorption spectrum of Congo red trans conf in 20 water in ethanol 27 Figure 13 Kinetic profile of Congo red in 20 water in ethanol 29 Figure 14 Absorption kinetic profile of Congo...

Page 4: ...each other Chemical kinetics is one of the major divisions of physical chemistry and is basically the quantitative study of the rates and mechanisms of chemical reactions Chemical change can be induce...

Page 5: ...d voltage waveform into temporal profile of A and fitting the A profile to an appropriate function in order to extract the rate constants can be done by exporting the data into Vernier Logger Pro soft...

Page 6: ...t Specifications Weight 10 lbs Footprint 8 x 8 20 3 cm x 20 3 cm UL94 rating V 0 Meets UL796 requirements Voltage range 100 120 V 210 240 V Frequency range 50 Hz 60 Hz Power rating 50 W maximum DC bat...

Page 7: ...formed with a 50 load unless stated otherwise Detector Silicon PIN Active area 3 6 x 3 6 mm 13 mm2 Wavelength range 350 to 1100 nm Peak wavelength p 970 nm Rise time tr 14 ns Bias voltage VR 10 V Dark...

Page 8: ...approximation of room temperature Do not disassemble the spectrometer case Doing so may result in damaging the excitation light source and electric shock If the spectrometer does not appear to be func...

Page 9: ...Software Technology 9 WARNING Situation has the potential to cause bodily harm or death NOTE Additional information the user or operator should consider CAUTION Situation has the potential to cause d...

Page 10: ...ystems LLC Vernier Software Technology 10 3 Layout and Basic Principles of Operation Figure 3 Schematic of the Vernier Flash Photolysis Spectrometer Detector photodiode F LED Digitizer Sample L1 L2 Xe...

Page 11: ...esired wavelength out of the broad emission spectrum of the LED While the continuous wave CW output from the LED is being monitored by the photodiode the photoexcitation flash is sent through the samp...

Page 12: ...evice Start the Vernier Flash Photolysis Spectrometer Software NOTE The 12 V battery that powers the photodiode can be accessed by removing the battery compartment lid on the side of the housing 4 2 O...

Page 13: ...the I0 value should drop close to zero 10 mV During data acquisition the Vernier Flash Photolysis Spectrometer will wait for approximately 2 seconds between flashes to allow enough time for the flash...

Page 14: ...default the cursor mode on the graph is y axis zoom with the following graph controls Axis Auto Scale mode OFF and ON Autoscale axis once Pan graph Select between graph zoom modes Select X and Y regi...

Page 15: ...the fundamental principles of chemical kinetics Now some necessary definitions 5 1 Stoichiometry Every chemical change can be represented by a stoichiometric or balanced equation in symbolic form For...

Page 16: ...at The rate of a chemical reaction is directly proportional to the active masses of the reacting species For reactions taking place in dilute homogeneous solution the term active masses can be replace...

Page 17: ...Equation 8 For this reaction it is seen that the concentration of A appears as the 2nd power and we say that the reaction is second order in A and second order overall Also the symbolic elementary pro...

Page 18: ...ontal lines one blue at 0 5 and one red at 0 37 The blue one is drawn at the point of 50 reaction half of the initial concentration of A has been converted into B By inspection this occurs after an el...

Page 19: ...has fallen to 36 8 about 37 of its initial value Note that in processes that are first order overall the half life and the life time are independent of time and initial concentration So far we have c...

Page 20: ...tion of one of the reacting species say B is very much higher than that of the other A then changes in concentration of B through reaction become negligible compared to those of A which go from 100 to...

Page 21: ...l need to transfer them to the Logger Pro or Excel for analysis For Figure 6 the raw data were imported into Logger Pro In cases where the voltage has been generated from an emission experiment no pro...

Page 22: ...This tells us that a species that absorbs light at the observation wavelength is generated by the flash and thus the resulting solution transmits less of the monitoring beam Except under certain condi...

Page 23: ...er when analyzing the kinetic profiles acquired with Vernier Flash Photolysis Spectrometer is the scattered excitation light recorded by the photodetector Figure 8 0 2 0 1 0 0 0 1 0 2 0 3 0 4 0 5 0 5...

Page 24: ...om Equations 11 and 12 and test the data against the transformed data In many spreadsheet programs including Logger Pro the requirement for the fitting transform is to express the absorbance as a func...

Page 25: ...and torsional excitations Since it is the electronic configuration of a molecule that governs its chemical properties excited electronic states show different chemical properties from their parent gro...

Page 26: ...vent Background Congo red CR is a diazo dye that is a derivative of azobenzene As can be seen from the skeletal structure in Figure 11 CR has two identically substituted azobenzene moieties Figure 11...

Page 27: ...pidly from a trans excited state to a cis ground state that is a higher energy state than the trans ground state This cis state is therefore metastable with respect to the trans ground state and in fl...

Page 28: ...ed in front of the detector If the I0 reading on the lower left of the Vernier Flash Photolysis Spectrometer Software is about 20 lower than the value without the cuvette in the sample position or wit...

Page 29: ...f this process that you are required to extract from the data set Repeat data collection with the averages set to 10 or more and save the resulting data Do the same procedure for the other samples you...

Page 30: ...Ultrafast Systems LLC Vernier Software Technology 30 Figure 14 Absorption kinetic profile of Congo red in 20 water in ethanol with 2 mM OH ions...

Page 31: ...of color can be catalyzed by acids and bases In this experiment the solution of the HgDz complex is excited by the flash lamp and the decay of the transient absorption at 600 nm is monitored as a fun...

Page 32: ...ing 3 mL of HgDz stock aliquots of TFA stock in the range of 0 1 mL and sufficient ethanol to bring total volume to 4 0 mL These sample solutions will all have the same concentration of HgDz and varyi...

Page 33: ...Ultrafast Systems LLC Vernier Software Technology 33 Figure 17 Trifluoroacetic acid TFA MW 114 03 Figure 18 Kinetic profile of mercury dithizonate in ethanol...

Page 34: ...romic reaction of 6 NO2 BIPS The N isomer is the thermodynamically more stable isomer and absorbs in the UV region whereas the MC isomer absorbs in both the UV and visible regions The MC isomer exhibi...

Page 35: ...Prepare a hot bath of water that can be temperature controlled and use a thermometer to monitor the temperature The bottom half of the cuvette should be placed into the hot bath to allow the solution...

Page 36: ...Ultrafast Systems LLC Vernier Software Technology 36 Figure 20 Ground state absorption spectrum of one spiropyran in toluene Figure 21 Transient absorption at 600 nm of spiropyran in toluene...

Page 37: ...Ultrafast Systems LLC Vernier Software Technology 37 Figure 22 Example decay and exponential fit for 55 C measurement Figure 23 Actual data example of ln as a function of 1000 T...

Page 38: ...Vernier Software Technology 38 8 Appendix 8 1 Spectra of Flash Lamp and White Light LED 200 300 400 500 600 700 800 0 0 0 2 0 4 0 6 0 8 1 0 Relative Irradiance Wavelength nm Figure 24 Emission spectr...

Page 39: ...Ultrafast Systems LLC Vernier Software Technology 39 400 500 600 700 0 0 0 2 0 4 0 6 0 8 1 0 Relative Irradiance Wavelength nm Figure 25 Emission spectrum of white light LED...

Page 40: ...s LLC Vernier Software Technology 40 8 2 Spectra of Optical Filters 550 560 570 580 590 600 610 620 630 640 650 0 10 20 30 40 50 60 wavelength nm Transmission Figure 26 Transmission spectrum of 600 nm...

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