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Troubleshooting
Summary of Contents for Ultrafast Systems KRONOS
- Page 2 Ultrafast Systems be liable for any direct, indirect, special, incidental or consequential damages resulting from any defects in this documentation. © 2022 Ultrafast Systems. All rights reserved. No part of this manual may be reproduced or copied without the prior written approval of Ultrafast Systems.
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Page 3: Table Of Contents
Hardware ......................10 Software ......................12 Using Kronos .......................15 7.1 Setting Up Kronos ....................15 7.2 Preparing Kronos for Experiments ................15 7.3 Choosing the Excitation and Detection Wavelengths ..........15 7.4 Acquiring Data .......................18 Familiarizing Yourself with the Reference Samples ..........20 8.1 Base Catalysis of the cis-trans Isomerization of Congo Red ........20 8.2 Determination of the Activation Energy of the Thermal Back Reaction of One... - Page 4 10.2 Photochemistry .....................29 10.3 Chemical Kinetics ....................30 10.3.1 Reaction Rate ......................30 10.3.2 Rate Expression and Rate Constant ................30 10.3.3 Order of Reaction ....................30 10.3.4 Experimental Approach ..................32 Maintenance and Troubleshooting ...............33 11.1 Maintenance ......................33 11.2 Troubleshooting ....................34 Appendix ......................35 Warranty ......................36 Limitation of Warranty ....................36 Notice ........................37 14.1 Confidentiality &...
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Page 5: Table Of Figures
(b) light blue or 400-700 colored glass excitation filters ............17 Figure 6: Transmission spectrum of 600 nm detection dielectric interference filter....18 Figure 7: Various reference samples used for different experiments in Kronos. The inset shows the full curve; note the strong spike due to the flash lamp..........19 Figure 9: Ground state absorption spectrum of Congo Red (trans conf.) in 20% water/ethanol. -
Page 6: Preface
Chemical change can be induced in a variety of ways; the one employed in Kronos is by absorption of light. Thus, the instrument serves also as a way of introducing the student to the concepts and practice of Photochemistry. -
Page 7: General Safety
• Read all warnings on the unit and in the operating instructions. • Kronos uses a large capacitor to charge the Xe flash lamp. Dangerous voltage levels are expected to persist even after unplugging the unit. • Do not disassemble or open the spectrometer case. Doing so may damage the excitation light source and risk electric shock. -
Page 8: Product Specifications
3. Product Specifications Table 1: Product specifications of Kronos. General Specifications Footprint (L x W) 135 mm x 105 mm Weight 1 kg UL94 UL796 Meets requirements USB cable 28 AWG shielded USB connection Power source Supplied current: 500 mA... - Page 9 Detector Specifications Detector type Silicon PIN 3.6 x 3.6 mm (13 mm Active area Wavelength range 350 to 1100 nm Rise time 14 ns Bias voltage 10 V...
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Page 10: Unpacking And Inspection
Figure 1: Spectral response of detector. Kronos produces a 2-dimensional Time-Current data matrix in a form of an ASCII (.CSV file) which can be easily processed with free or commercially available spreadsheet or graphing software, e.g. Microsoft Excel, OriginLab Origin, etc. -
Page 11: Hardware
5. Hardware The Kronos is shown in Figure 2a and b, highlighting the simple design that makes Kronos very easy to use. Holes are machined into the housing which allows rapid replacements of standard square filters and cuvettes. The detection filters are mounted in a customized holder. Figure 2c shows the simplified optical layout of the Kronos. - Page 12 Table 3: Excitation colored glass filters included with the Kronos. Excitation colored glass filters transmitted wavelengths (nm): 300-450 + >700 400-700 Table 4: Detection dielectric interference filters included with the Kronos with center wavelengths listed. Detection dielectric interference filters, 10 nm bandwidth, center lines at (nm):...
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Page 13: Software
6. Software Table 5: UI elements in the Kronos software. ELEMENT DESCRIPTION Photodiode I Amount of probe light reaching the photodiode (Probe intensity, y-axis) Related to detector gain and LED intensity Range Absorption mode: Leave it on Auto Emission mode: Adjust the range slider to achieve sufficient signal-to-noise... -
Page 14: Figure 3: Screenshot Of The Kronos Software
Figure 3: Screenshot of the Kronos software. Figure 3 shows the Kronos UI. By default, the software will adjust the axis scales automatically: the Y-axis range will adjust to display the signal only, showing the large spike around time = 0. The default X-axis setting is “Auto Scale”. - Page 15 Table 6: Graph controls in Kronos. ELEMENT DESCRIPTION Axis Autoscale mode OFF and ON Autoscale axis once Pan graph Select between graph zoom modes: Select X and Y region to zoom in Select X region to zoom in, keep Y limits unchanged Select Y region to zoom in, keep X limits unchanged (default) Autoscale both X and Y axes once to fit graph...
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Page 16: Using Kronos
7.3 Choosing the Excitation and Detection Wavelengths Kronos uses a Xe lamp and LED for the pump and probe light, respectively. Both are broadband light sources and their spectra is shown in Figure 4. By using an appropriate filter, one of the square colored glass filters, you can select which wavelength to pump (excite) the sample with,... -
Page 17: Figure 4: Spectra Of Kronos Light Sources
Figure 4: Spectra of Kronos light sources: (a) Xenon flash lamp for the pump (b) LED for the probe. -
Page 18: Figure 5: Transmission Spectrum Of
Figure 5 shows the transmission spectra of the two colored glass filters included with Kronos. Any incident light within the high transmittance regions can pass through the filters easily. For example, the dark blue filter, 300-450 nm + >700 nm, has high transmittance around 350 nm and allows the Xe lamp to function as a UV/blue light source. -
Page 19: Acquiring Data
The detection wavelength range is manually selected by using a 0.5” bandpass filter. The labeled broad rectangular slit on top of the Kronos housing accommodates one such filter mount. Figure 6 shows the transmission spectrum of the 600 nm bandpass filter included with Kronos. These filters have a bandwidth, or full width at half maximum of 10 nm (in this scenario, 595 nm to 605 nm). -
Page 20: Figure 7: Various Reference Samples Used For Different Experiments In Kronos. The Inset Shows
(amperes). A sample graph is shown in Figure 7. Figure 7: Various reference samples used for different experiments in Kronos. The inset shows the full curve; note the strong spike due to the flash lamp. -
Page 21: Familiarizing Yourself With The Reference Samples
Sodium hydroxide, ethanol Toluene chemicals Table 7 shows the various standard experiments that are possible with Kronos. This section serves to provide experiment ideas for the user. 8.1 Base Catalysis of the cis-trans Isomerization of Congo Red The absorption spectrum of a solution of CR in its trans-ground state in 20% water/ethanol is... -
Page 22: Figure 9: Ground State Absorption Spectrum Of Congo Red (Trans Conf.) In 20% Water/Ethanol
Figure 9: Ground state absorption spectrum of Congo Red (trans conf.) in 20% water/ethanol. When excited, the electronic structure of the dye shifts, causing the –N=N- bond to become torsionally flexible. This causes CR to flip rapidly and lose the imparted energy. CR goes from a trans-excited state to a cis-ground state that is still at a higher energy state than the trans-ground state. -
Page 23: Figure 10: Kinetic Profile Of Congo Red In 20% Water In Ethanol
The flash induces a fast photochemical response, much faster than what the Kronos can resolve, and subsequently generates the ground state of the cis-form. This absorbs light, causing the detector to register a drop in transmission. Then, the excited cis-state returns to the trans-state ground-state over many milliseconds. -
Page 24: Determination Of The Activation Energy Of The Thermal Back Reaction Of One Spiropyran In Toluene
Figure 11: Calculated and fitted ΔA plot. 8.2 Determination of the Activation Energy of the Thermal Back Reaction of One Spiropyran in Toluene This section uses a scientific publication for reference: Piard, Jonathan, “Influence of the Solvent on the Thermal Back Reaction of One Spiropyran” Journal of Chemical Education. 2014, 91, 2105-2111. -
Page 25: Figure 12: Structure And Photochromic Reaction Of 6-No-Bips
Figure 12: Structure and photochromic reaction of 6-NO -BIPS. In this experiment, the kinetics of the back reaction will be measured for a range of temperatures in order to determine the activation energy, E , of the back reaction. The literature reported value for E = 62.5 kJ mol . -
Page 26: Figure 14: Transient Absorption Of Spiropyran In Toluene At 600 Nm Detection Wavelength
Prepare a 5.0 × 10 M solution of 6-NO -BIPS in toluene. Using a hot bath, record the absorption −6 of the sample with 5 different temperatures between 30 and 60 °C. Figure 14 shows an example of measurements done at five varying temperatures. Figure 14: Transient absorption of Spiropyran in Toluene at 600 nm detection wavelength. -
Page 27: Figure 15: Example Decay And Exponential Fit For 55°C Measurement
Figure 15: Example decay and exponential fit for 55°C measurement. Figure 16: Actual data example of ln(τ) as a function of 1000/T. -
Page 28: Operation Of Kronos
9. Operation of Kronos 9.1 Start-Up Switch on the Kronos. The LED will start immediately, and you should be able to see a white glow inside the enclosure Start the Kronos software 9.2 Choose Experiment Mode and Set Parameters Choose Absorption or Emission mode for your experiments Set the number of times to average and the time window 9.3 Finding the Signal... -
Page 29: Basic Theory
‘fast’ pulsed light source and an appropriate detector is sufficient. TA spectroscopy is also known as pump-probe spectrometry: the pump (in Kronos, the flash lamp) excites the sample and generates photogenerated carriers that is the interrogated by the probe... -
Page 30: Photochemistry
light (LED). The goal is to measure the pump-induced probe change. By taking the difference between the transmitted and initial signal, and doing a logarithmic calculation, the change in absorption [ΔA] at a particular wavelength can be obtained, In such measurements, kinetics data is represented in signal vs relative time units, e.g. delay time. The data is relative to a quantity called ‘time zero’. -
Page 31: Chemical Kinetics
10.3 Chemical Kinetics 10.3.1 Reaction Rate The rate of a chemical reaction is expressed as the variation with time of the concentration of either reactants or products. In solution phase reactions, as studied here, the units of reaction rate are concentration units per second, i.e. mole per liter per second, M s . −1 In the (elementary) reaction, A + B ⟶... - Page 32 first order in [A] and overall first order. Orders higher than 2, fractional and zero orders are found in special cases. These are not considered here because they are not relevant to Kronos. NOTE: It is important to realize that assignment of order by inspection is only valid for elementary...
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Page 33: Experimental Approach
10.3.4 Experimental Approach The data that are obtained in a kinetics experiment could look something like those shown in Figure 18. The change in concentration of reactant A (open circles) and product B (filled circles) as a function of time can be observed; M relative concentration of the species (A or B). Figure 18: Concentration time profiles of reactant and product. -
Page 34: Maintenance And Troubleshooting
11. Maintenance and Troubleshooting 11.1 Maintenance Kronos does not contain any consumable items or spare parts. The exterior of Kronos can be cleaned with a soft cloth moisten with ethanol. Never use acetone. Replace the lids to ensure no contaminants or dust will fall into the modules. Avoid cleaning inside the modules due to the risk of optics and crystal contamination, and accidental misalignment. -
Page 35: Troubleshooting
Here’s what to do… Plug the USB connector in snugly and check that the There is no white glow in the Kronos when computer can detect the Kronos. It will appear as a COM the USB is plugged in. port connection. -
Page 36: Appendix
12. Appendix The Kronos software has an advanced settings window for experienced users. The settings can be accessed by pressing CTRL + SHIFT + C on the keyboard from the main window of the Kronos software. In this window, you can change the COM port and the default graphing unit from current to ΔA. -
Page 37: Warranty
If the Product is found to be defective during the warranty period, the Product will either be repaired or replaced at Ultrafast Systems’ option. To exercise this warranty, write to or call your local Ultrafast Systems office or representative, or contact Ultrafast Systems headquarters in Sarasota, Florida. You will be given prompt assistance and return instructions. -
Page 38: Notice
The Ultrafast Systems programs and all materials furnished or produced in connection with them ("Related Materials") contain trade secrets of Ultrafast Systems and are for use only in the manner expressly permitted. Ultrafast Systems claims and reserves all rights and benefits afforded under law in the Programs provided by Ultrafast Systems.
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