Ultrafast Systems KRONOS User manual

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Table of Contents
Table of Contents ........................................................................................................2
Table of Figures ..........................................................................................................4
1. Preface .................................................................................................................5
2. General Safety .......................................................................................................6
2.1 Hazards ...................................................................................................................6
2.2 Electrical Safety .......................................................................................................6
3. Product Specifications ...........................................................................................7
4. Unpacking and Inspection ......................................................................................9
5. Hardware ............................................................................................................10
6. Software .............................................................................................................12
7. 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
8. 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
Spiropyran in Toluene .............................................................................................23
9. Operation of Kronos .............................................................................................27
9.1 Start-Up .................................................................................................................27
9.2 Choose Experiment Mode and Set Parameters .........................................................27
9.3 Finding the Signal ..................................................................................................27
9.4 Acquiring Data .......................................................................................................27
9.5 Shutdown ..............................................................................................................27
10. Basic Theory .......................................................................................................28
10.1 Transient Optical Spectrometry ..............................................................................28
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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
11. Maintenance and Troubleshooting .......................................................................33
11.1 Maintenance .........................................................................................................33
11.2 Troubleshooting ....................................................................................................34
12. Appendix ............................................................................................................35
13. Warranty .............................................................................................................36
Limitation of Warranty ...................................................................................................36
14. Notice ................................................................................................................37
14.1 Confidentiality & Proprietary Rights ........................................................................37
14.1.1 Reservation of Title ...............................................................................................37
14.1.2 Preservation of Secrecy and Confidentiality and Restrictions to Access ...................37
14.2 Service Information ...............................................................................................37
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Table of Figures
Figure 1: Spectral response of detector. ....................................................................................9
Figure 2: 3D render of Kronos .................................................................................................10
(a) without components inserted .........................................................................................10
(b) fully loaded with a cuvette, excitation, and detection filters ..............................................10
(c) Schematic optical layout of the Kronos ...........................................................................10
Figure 3: Screenshot of the Kronos software. ..........................................................................13
Figure 4: Spectra of Kronos light sources: ...............................................................................16
(a) Xenon flash lamp for the pump .......................................................................................16
(b) LED for the probe. ..........................................................................................................16
Figure 5: Transmission spectrum of ........................................................................................17
(a) dark blue or 350-400 + >700 ...........................................................................................17
(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. ..21
Figure 10: Kinetic profile of Congo Red in 20% water in ethanol. ...............................................22
Figure 11: Calculated and fitted ΔA plot. .................................................................................23
Figure 12: Structure and photochromic reaction of 6-NO-BIPS. .................................................24
Figure 13: Ground state absorption spectrum of One Spiropyran in toluene. ..............................24
Figure 14: Transient absorption of Spiropyran in Toluene at 600 nm detection wavelength. ........25
Figure 15: Example decay and exponential fit for 55°C measurement. .......................................26
Figure 16: Actual data example of ln(τ) as a function of 1000/T. ..............................................26
Figure 17: Photophysical and photochemical sequence in light-matter interactions. ..................29
Figure 18: Concentration time profiles of reactant and product. ................................................32
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1. Preface
This document contains user information for the Kronos flash photolysis spectrometer. Kronos is
conceived to be a simple, user-friendly device for demonstrating to chemistry students the
fundamental principles of Chemical Kinetics. Every process labeled as “chemical” occurs as the
result of chemical bonds being broken or formed, i.e. nuclei change their spatial positions with
respect to 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 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.
Read this Documentation carefully before operating the spectrometer for the first time. Special
attention should be given to Section 2: General Safety.
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2. General Safety
The Kronos flash photolysis spectrometer is designed and manufactured for kinetic analysis of
chemical specimen by means of ultrafast transient absorption spectrometry. And it is not sold, nor
intended for, nor should ever be used for any other purpose. The product should be used solely in
accordance with the instructions provided.
2.1 Hazards
Take extra caution when operating or servicing this equipment:
•If this equipment is used in a manner not specified in this manual, the protection provided by
this equipment may be impaired.
•Handle the cuvette with care. Check the cuvette for damage or cracks and replace any damaged
ones immediately.
•Use extreme caution in handling the cuvette when it is filled with liquid. Always remove the
cuvette before changing contents. Never fill or refill the cuvette when it is in the sample holder.
•The optimal operation temperature of Kronos is at or near room temperature.
2.2 Electrical Safety
Observe these general warnings when operating or servicing this equipment:
•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.
•Do not use this equipment in or near water.
•Dry the exterior of the cuvette prior to placing it in the holder. Using a cuvette with a wet exterior
or one that is leaking liquid can result in malfunction, shorting of electrical components or
electric shock.
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3. Product Specifications
Table 1: Product specifications of Kronos.
General Specifications
Footprint (L x W)
135 mm x 105 mm
Weight
1 kg
UL94
V-0
UL796
Meets requirements
USB cable
28 AWG shielded
Power source
USB connection
Supplied current: 500 mA
Supplied voltage: 5 V
Operating temperature
15 to 40 °C
Operating relative humidity
10 to 70% (non-condensing)
Spectrometer Specifications
Spectral coverage
450 -750 nm
Spectral resolution
Depends on the filter used. Typically, ~10 nm
Temporal resolution
~100 μs
Time window
≥ 15 ms
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Detector Specifications
Detector type
Silicon PIN
Active area
3.6 x 3.6 mm (13 mm2)
Wavelength range
350 to 1100 nm
Rise time
14 ns
Bias voltage
10 V
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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.
4. Unpacking and Inspection
The Kronos spectrometer is carefully packaged at the factory to minimize the possibility of
damage during shipping. Inspect the box for external signs of damage or mishandling. Inspect the
contents for damage. If there is visible damage to the instrument upon receipt, inform the shipping
company and Ultrafast Systems immediately.
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