Time-Resolved Fluorescence Wiki

measuring_quantum_yield

Anonymous (anonymous@undisclosed.example.com) — 2017-07-12T13:16:44+00:00

2017/07/12 15:13		current
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	{{ youtube>JLiDnlS5BS8?large }}		{{ youtube>JLiDnlS5BS8?large }}

-	===== Setp-by-Step =====	+	===== Step-by-Step =====
-	* Insert the integrating sphere with caution in order not to hit any optical elements in the FluoTime 300. The integrating sphere assembly has an indexed lid to ensure proper orientation.	+	* Mount the integrating sphere carefully. Make sure you do not hit any optical elements inside the FluoTime 300. The integrating sphere assembly has an indexed lid to ensure proper orientation.

	{{ :howto:2013-12-19_at_14-30-03.jpg?600 \|}}		{{ :howto:2013-12-19_at_14-30-03.jpg?600 \|}}

fluorescence_correlation_spectroscopy-_a_short_introduction

Anonymous (anonymous@undisclosed.example.com) — 2024-10-11T08:30:57+00:00

2023/02/17 13:43		current
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	{{tag>MicroTime LSM Theory SymPhoTime FCS Correlation}}		{{tag>MicroTime LSM Theory SymPhoTime FCS Correlation}}

-	~~TOC~~	+

	====== Introduction to Fluorescence Correlation Spectroscopy ======		====== Introduction to Fluorescence Correlation Spectroscopy ======

novaflim_calculated_irf

Anonymous (anonymous@undisclosed.example.com) — 2025-03-11T08:19:29+00:00

2025/02/18 14:49		current
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	====== NovaFLIM Calculated IRF ======		====== NovaFLIM Calculated IRF ======
		+	{{tag> faq software novaflim IRF}}
		+

	In the Nova Flim the IRF is parameterized as a combination of two Gaussian curves (a total of 5 fit parameters). These parameters are adjusted during Initial Fit.		In the Nova Flim the IRF is parameterized as a combination of two Gaussian curves (a total of 5 fit parameters). These parameters are adjusted during Initial Fit.

some_origins_of_multiexponetial_decays_for_single_dyes

Anonymous (anonymous@undisclosed.example.com) — 2019-03-19T12:31:43+00:00

pattern_matching

Anonymous (anonymous@undisclosed.example.com) — 2014-06-18T13:26:07+00:00

2014/05/23 09:39		current
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	Pattern Matching Analysis by decomposing a recorded image into different user-defined patterns. Display of the calculated data using an RGB false color model. The calculated amplitudes of the first three defined patterns are depicted in three different colors for each pixel.		Pattern Matching Analysis by decomposing a recorded image into different user-defined patterns. Display of the calculated data using an RGB false color model. The calculated amplitudes of the first three defined patterns are depicted in three different colors for each pixel.
		+
		+	{{ youtube>L68IgRbNSLE?large }}

	==== Open an Image ====		==== Open an Image ====

interfacing_time_resolved_spectrometer_fluotime_300_microscope_microtime_100

Anonymous (anonymous@undisclosed.example.com) — 2020-05-18T14:19:46+00:00

2020/05/18 16:19		current
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-	{{tag> video FT300 easyTau MT100 FLIM microscopy howto tutorial draft}}	+	{{tag> video FT300 easyTau MT100 FLIM microscopy howto tutorial}}

	====== Interfacing a time-resolved spectrometer (FluoTime 300) with a microscope (MicroTime 100) ======		====== Interfacing a time-resolved spectrometer (FluoTime 300) with a microscope (MicroTime 100) ======

lifetime_component_decomposition_phasor_plot_analysis

Anonymous (anonymous@undisclosed.example.com) — 2025-06-16T07:17:47+00:00

2025/06/16 09:17		current
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	* Sample information:		* Sample information:
-	* Daisy Pollen	+	* Daisy pollen
		+
		+	---

	* Software information: NIS-Elements version 5.42.06 with PicoQuant FLIM-FCS full integration		* Software information: NIS-Elements version 5.42.06 with PicoQuant FLIM-FCS full integration
	{{:lifetime_component_decomposition_in_phasor_plot.mp4?1000\|}}		{{:lifetime_component_decomposition_in_phasor_plot.mp4?1000\|}}
-		+
	* Sample information:		* Sample information:
	* Glial Fibrillary Acidic Protein (GFAP) — labeled with BDP-TMR		* Glial Fibrillary Acidic Protein (GFAP) — labeled with BDP-TMR
	* Mitochondria (via TOM20) — labeled with CY3		* Mitochondria (via TOM20) — labeled with CY3

2ffcs

Anonymous (anonymous@undisclosed.example.com) — 2015-11-04T09:41:00+00:00

2014/04/09 22:02		current
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	Correlation analysis that is applied to the fluctuations of the fluorescence intensity. The cross-correlation between the occurrence of events in two different detection volumes is used to introduce an absolute diffusion length into the analysis.		Correlation analysis that is applied to the fluctuations of the fluorescence intensity. The cross-correlation between the occurrence of events in two different detection volumes is used to introduce an absolute diffusion length into the analysis.
		+
		+	see [[glossary:FCS]] for a introduction on FCS.

	===== Experimental Setup =====		===== Experimental Setup =====

align_beam_backreflection

Anonymous (anonymous@undisclosed.example.com) — 2022-08-29T11:17:12+00:00

2022/08/29 13:15		current
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	Adding a drop of water on top of the coverslip reduces the back-scattering intensity by an order of magnitude or so, but the basic shape remains the same. Even if one removes everything extra from the beam path, these fringes remain there, they are universal. Note that all those images above are slightly defocused.		Adding a drop of water on top of the coverslip reduces the back-scattering intensity by an order of magnitude or so, but the basic shape remains the same. Even if one removes everything extra from the beam path, these fringes remain there, they are universal. Note that all those images above are slightly defocused.

-	Such images are used for the daily and fundamental alignment of the MicroTime 200. The detailed procedure is described in the user manual of MicroTime 200. Although the MicroTime is extremely robust we suggest to spend 5-10 minutes every day for verifying the quality of the alignment by inspecting the back-reflection pattern. Have a look how this is used also by watching the tutorial [[howto:exchange_dichroic_mt200\|How to exchange the main dichroic of the MicroTime 200.]]	+	Such images are used for daily and fundamental alignment of the MicroTime 200. A detailed procedure is described in the user manual of MicroTime 200. Although MicroTime is extremely robust, we suggest to spend 5-10 minutes every day for verifying the quality of the alignment by inspecting the back-reflection pattern. Have a look how this is used also by watching the tutorial [[howto:exchange_dichroic_mt200\|How to exchange the main dichroic of the MicroTime 200.]]

	The paper by [[ http://rspa.royalsocietypublishing.org/content/253/1274/358\|B. Richards and E. Wolf: Electromagnetic diffraction in optical systems, II. Structure of the image field in an aplanatic system]] shows such 4 lobed patterns for polarized light.		The paper by [[ http://rspa.royalsocietypublishing.org/content/253/1274/358\|B. Richards and E. Wolf: Electromagnetic diffraction in optical systems, II. Structure of the image field in an aplanatic system]] shows such 4 lobed patterns for polarized light.

	Similar figures can be found in this [[https://books.google.cz/books?id=kURdAAAAQBAJ\|classic textbook]].		Similar figures can be found in this [[https://books.google.cz/books?id=kURdAAAAQBAJ\|classic textbook]].

diamond_nv_centers

Anonymous (anonymous@undisclosed.example.com) — 2018-04-19T12:11:55+00:00

2018/04/19 14:11		current
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	see also [[wp>Nitrogen-vacancy center]]		see also [[wp>Nitrogen-vacancy center]]

-	{{ howto:model_nv-centers.png\|Figure1: Model of the nitrogene vacancy in the diamond lattice}}	+	[{{ howto:model_nv-centers.png\|Figure1: Model of the nitrogene vacancy in the diamond lattice}}]

	==== Excitation ====		==== Excitation ====

how_to_measure_the_instrument_response_function_irf

Anonymous (anonymous@undisclosed.example.com) — 2023-09-07T22:55:03+00:00

2023/09/08 00:54		current
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	===== Using samples with ultrafast decay =====		===== Using samples with ultrafast decay =====

-	Some detectors (particularly SPADs) have wavelength dependent timing response. In this case an IRF recorded at the excitation wavelength may not be useful for precise reconvolution. The solution is to acquire the IRF at the fluorescence wavelength, or at least spectrally closer to the fluorescence emission.	+	Some detectors (particularly MPD SPADs) have a wavelength dependent timing response. In this case an IRF recorded at the excitation wavelength may not be useful for precise reconvolution. The solution is to acquire the IRF at the fluorescence wavelength, or at least spectrally closer to the fluorescence emission wavelength.

	==== General recipe ====		==== General recipe ====

how_to_work_with_the_instrument_response_function_irf

Anonymous (anonymous@undisclosed.example.com) — 2023-02-17T12:41:49+00:00

2021/03/23 11:49		current
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-	{{tag>howto IRF tutorial analysis MT LSM_upgrade}}	+	{{tag>howto IRF tutorial analysis MicroTime LSM_upgrade}}

intensity_time_trace_analysis

Anonymous (anonymous@undisclosed.example.com) — 2014-06-19T08:12:32+00:00

2014/06/19 10:12		current
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	{{tag> tutorial howto time-trace analysis SymPhoTime}}		{{tag> tutorial howto time-trace analysis SymPhoTime}}

-	~~TOC~~	+	~~NOTOC~~

	======Intensity Time Trace Analysis======		======Intensity Time Trace Analysis======

select_the_correct_pinhole_size

Anonymous (anonymous@undisclosed.example.com) — 2015-09-11T15:24:14+00:00

2015/09/11 17:22		current
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	====== How-to select the correct pinhole size ======		====== How-to select the correct pinhole size ======

-	The pinhole size should be slightly bigger than the image of the [[https://en.wikipedia.org/wiki/Airy_disk\|Airy Disc]] at the position of the pinhole:	+	The pinhole size should be slightly bigger than the image of the [[wp>Airy Disc]] at the position of the pinhole:

	$$d_{Airy} = (1.22 * lambda / N.A.) * M$$		$$d_{Airy} = (1.22 * lambda / N.A.) * M$$

using_the_antibunching_script

Anonymous (anonymous@undisclosed.example.com) — 2014-06-19T07:40:32+00:00

2014/06/19 09:36		current
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	{{tag> antibunching howto tutorial correlation analysis SymPhoTime}}		{{tag> antibunching howto tutorial correlation analysis SymPhoTime}}
-	~~TOC~~	+	~~NOTOC~~

	====== Antibunching Analysis ======		====== Antibunching Analysis ======
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	This tutorial shows step-by-step, how to calculate an antibunching curve from a fluorescence time trace of a single emitter, in this example a nanodiamond NV center, excited with a pulsed 530 nm laser.		This tutorial shows step-by-step, how to calculate an antibunching curve from a fluorescence time trace of a single emitter, in this example a nanodiamond NV center, excited with a pulsed 530 nm laser.
		+
		+	{{ youtube>bEyhuWnmFC4?large }}

	===== Background Information =====		===== Background Information =====
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	* Here it is impossible to determine the number of emitters. In this measurement the luminescence stems from several emitters.		* Here it is impossible to determine the number of emitters. In this measurement the luminescence stems from several emitters.
-

microtime

Anonymous (anonymous@undisclosed.example.com) — 2015-11-03T14:24:05+00:00

2015/11/03 15:23		current
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	* Turn-key diode lasers for multicolor excitation from 375 nm to 900 nm		* Turn-key diode lasers for multicolor excitation from 375 nm to 900 nm
	* Up to 4 truly parallel detection channels using application-optimized detection with [[glossary:SPAD]]s, [[glossary:PMT]]s or [[glossary:Hybrid PMT]]s		* Up to 4 truly parallel detection channels using application-optimized detection with [[glossary:SPAD]]s, [[glossary:PMT]]s or [[glossary:Hybrid PMT]]s
-	* Time-Correlated-Single Photon Counting ([[glossary:TCSPC]]) and [[glossary:TTTR]] mode for investigation of fast dynamics in FCS and FLIM	+	* Time-Correlated-Single Photon Counting ([[glossary:TCSPC]]) and [[glossary:TTTR]] mode for investigation of fast dynamics in [[glossary:FCS]] and [[glossary:FLIM]]
	* Piezo scanning for 2D- and 3D-lifetime imaging and accurate point positioning		* Piezo scanning for 2D- and 3D-lifetime imaging and accurate point positioning
	* Two optional exit ports for additional hardware, e.g. spectrographs		* Two optional exit ports for additional hardware, e.g. spectrographs

symphotime64

Anonymous (anonymous@undisclosed.example.com) — 2015-01-22T14:39:59+00:00

2014/05/23 09:34		current
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-	The [[http://www.picoquant.com\|PicoQuant]] SymPhoTime 64 software package is an integrated solution for data acquisition and analysis using PicoQuant's time-resolved confocal microscope MicroTime 200, LSM upgrade kits or [[glossary:TCSPC]] electronics. Its clearly structured layout and powerful analysis routines allows the user to focus on the results rather than on the data processing. The software is designed for a 64 bit operation system and features a graphical user interface (GUI), which guides the user through all necessary steps for an individual analysis or measurement process. Data dependencies are directly visible in the underlying workspace concept. An integrated scripting language ("STUPSLANG") even puts the user in a position to freely add new analysis procedures or customize existing ones.	+	The [[http://www.picoquant.com\|PicoQuant]] SymPhoTime 64 software package is an integrated solution for data acquisition and analysis using PicoQuant's time-resolved confocal microscope [[products:MicroTime]], LSM upgrade kits or [[glossary:TCSPC]] electronics. Its clearly structured layout and powerful analysis routines allows the user to focus on the results rather than on the data processing. The software is designed for a 64 bit operation system and features a graphical user interface (GUI), which guides the user through all necessary steps for an individual analysis or measurement process. Data dependencies are directly visible in the underlying workspace concept. An integrated scripting language ("STUPSLANG") even puts the user in a position to freely add new analysis procedures or customize existing ones.

	For more information, latest version and download link see [[http://www.picoquant.com/products/category/software/symphotime-64-fluorescence-lifetime-imaging-and-correlation-software\|SymPhoTime64]].		For more information, latest version and download link see [[http://www.picoquant.com/products/category/software/symphotime-64-fluorescence-lifetime-imaging-and-correlation-software\|SymPhoTime64]].

burst_duration_and_fcs_diffusion_time

Anonymous (anonymous@undisclosed.example.com) — 2026-01-12T14:58:02+00:00

2026/01/12 15:56		current
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	Gopich, I. V.; Szabo, A. Journal of Chemical Physics 2005, 122, 014707.		Gopich, I. V.; Szabo, A. Journal of Chemical Physics 2005, 122, 014707.

-	Ruttinger, S. Dissertation, 2006.	+	Ruettinger, S. Dissertation, 2006.

-	Dorr, D. Dissertation, 2014.	+	Doerr, D. Dissertation, 2014.

phasor_plot_structure_separation

Anonymous (anonymous@undisclosed.example.com) — 2025-06-16T08:36:34+00:00

2025/06/16 10:36		current
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	{{tag> FLIM acquisition Nikon AX Phasor video LSM_upgrade howto}}		{{tag> FLIM acquisition Nikon AX Phasor video LSM_upgrade howto}}

-	====== Phasor-Based Structural Separation Using FLIM ======	+	====== Nikon AX: Phasor-Based Structural Separation Using FLIM ======

	Introduction		Introduction

2019/03/06 13:44		current
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-	The fluorescence lifetime of a dye measured with a TCSPC spectrometer can be multiexponential due to many reasons. The most obvious cases are due to scattering or presence of impurities. Although less obvious, it is also widely known that in an inhomogeneous media a pure dye will also exhibit a multiexponential decay. Advanced users know that if the decay is not measured with polarizers at magic angle, the rotation correlation time shows up as a second exponential in the decay (the second exponential is in fact the product of the rotation correlation time by the fluorescence lifetime, divided by their sum). And they also know that measuring without polarizers is not equivalent to measure at magic angle... But suspicion may arise when even a pure dye measured at magic angle in a homogeneous media exhibits a multiexponential decay. Is the spectrometer properly adjusted? Are the polarizers properly calibrated? A typical mistake is to measure the [[glossary:IRF]] at the nominal laser wavelength instead of measuring at the ideal wavelength for that specific laser head. Note that all diode lasers heads emit at slightly different wavelengths and each of them have an optimum at which the IRF should be measured. As little as 0.5 nm displacement from their optimum may induce a "non perfect" [[glossary:deconvolution]] fit.	+	The fluorescence lifetime of a dye measured with a TCSPC spectrometer can be multiexponential due to many reasons. The most obvious cases are due to scattering or presence of impurities. Although less obvious, it is also widely known that in an inhomogeneous medium a pure dye will also exhibit a multiexponential decay. Advanced users know that if the decay is not measured with polarizers at magic angle, the rotation correlation time shows up as a second exponential in the decay (the second exponential is in fact the product of the rotation correlation time and the fluorescence lifetime, divided by their sum). And they also know that measuring without polarizers is not equivalent to measuring at magic angle... But suspicion may arise when even a pure dye measured at magic angle in a homogeneous medium exhibits a multiexponential decay. Is the spectrometer properly adjusted? Are the polarizers properly calibrated? A typical mistake is to measure the [[glossary:IRF]] at the nominal laser wavelength instead of measuring at the ideal wavelength for that specific laser head. Note that all diode lasers heads emit at slightly different wavelengths and each of them have an optimum at which the IRF should be measured. As little as 0.5 nm displacement from their optimum may induce a "non perfect" [[glossary:deconvolution]] fit.

	But it is worth noting that even at magic angle in a perfectly aligned spectrometer pure dyes in homogeneous media may exhibit a multiexponential decay. The origin may be physical, like solvent relaxation, or chemical, when the fluorescent molecule undergoes a ground or excited state reaction. In this brief article a few examples are described.		But it is worth noting that even at magic angle in a perfectly aligned spectrometer pure dyes in homogeneous media may exhibit a multiexponential decay. The origin may be physical, like solvent relaxation, or chemical, when the fluorescent molecule undergoes a ground or excited state reaction. In this brief article a few examples are described.
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-	The electronic redistribution of electrons due to optical excitation leads in many cases to a different reactivity in the ground and excited states. In other words, a fluorescent molecule which is boring under the dark may become reactive upon excitation. Common excited state reactions are redox (electron transfer) and acid-base (proton transfer) reactions. Depending on the rate of the excited-state rection relative the the original fluorescence lifetime, the observed decay time measured with a TCSPC spectrometer may be single- or multiexponential.	+	The electronic redistribution of electrons due to optical excitation leads in many cases to a different reactivity in the ground and excited states. In other words, a fluorescent molecule which is mostly inert in the dark may become reactive upon excitation. Common excited state reactions are redox (electron transfer) and acid-base (proton transfer) reactions. Depending on the rate of the excited-state reaction relative the the original fluorescence lifetime, the observed decay time measured with a TCSPC spectrometer may be single- or multiexponential.

	Let us consider the reaction in Scheme 2 in different situations:		Let us consider the reaction in Scheme 2 in different situations:
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	Scheme 2		Scheme 2

-	//Starting point: The molecule A is promoted to the excited-state where it can react with a molecule X to form the compound B, through a rate constant $k_{AB}$. Once the compound B is formed the back-reaction can occur, with a rate constant $k_{BA}$. Compounds A and B are fluorescent with original fluorescence lifetimes $\tau_A$ and $\tau_B$. Once B decays to the ground state the back-reaction takes place. Hence the system is always in its starting position $(A + X)$ prior to any excitation pulse.//	+	//Starting point: The molecule A is promoted to the excited-state where it can react with a molecule X to form the compound B, through a rate constant $k_{AB}$. Once the compound B is formed, the back-reaction can occur with a rate constant $k_{BA}$. Compounds A and B are fluorescent with original fluorescence lifetimes $\tau_A$ and $\tau_B$. Once B decays to the ground state, the back-reaction takes place. Hence the system is always in its starting position $(A + X)$ prior to any excitation pulse.//

	//Case A) The constant kAB is too slow with respect to $\tau_A$ and $\tau_B$.// In this case the compound A would decay to the ground-sate before the excited-state reaction could take place. The decay measured would be single exponential and coincident with $\tau_A$.		//Case A) The constant kAB is too slow with respect to $\tau_A$ and $\tau_B$.// In this case the compound A would decay to the ground-sate before the excited-state reaction could take place. The decay measured would be single exponential and coincident with $\tau_A$.
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	being $Z = \sqrt{(M-Y)^2 + 4 k_{AB} k_{BA}[x]}$		being $Z = \sqrt{(M-Y)^2 + 4 k_{AB} k_{BA}[x]}$

-	$A_1= A_0 [M- (1/\tau_2)] / [(1/\tau_1 – 1/\tau_2]$	+	$A_1= A_0 [M- (1/\tau_2)] / [1/\tau_1 – 1/\tau_2]$

-	$A_2= A_0 [(1/\tau_1)- M] / [(1/\tau_1 – 1/\tau_2]$	+	$A_2= A_0 [(1/\tau_1)- M] / [1/\tau_1 – 1/\tau_2]$

-	$B_1= -A_0 k_{AB}[x] / [(1/\tau_1 – 1/\tau_2]$	+	$B_1= -A_0 k_{AB}[x] / [1/\tau_1 – 1/\tau_2]$

-	$B_2= A_0 k_{AB} [x] / [(1/\tau_1 – 1/\tau_2]$	+	$B_2= A_0 k_{AB} [x] / [1/\tau_1 – 1/\tau_2]$

	being $A_0$ the concentration of $A$ at $t=0$.		being $A_0$ the concentration of $A$ at $t=0$.
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	Note from $A(t)$ that, even if $B$ would not be fluorescent, the decay of $A$ will still be biexponential!		Note from $A(t)$ that, even if $B$ would not be fluorescent, the decay of $A$ will still be biexponential!

-	A situation like this may occur with molecules dissolved in an aprotic but hygroscopic media, like acetonirile. Water molecules may diffuse (diffusion happens in the nanosecond time scale) and react with fluorophores bearing proton-transfer groups like -OH or -NH2.	+	A situation like this may occur with molecules dissolved in an aprotic but hygroscopic medium, like acetonitrile. Water molecules may diffuse (diffusion happens in the nanosecond time scale) and react with fluorophores bearing proton-transfer groups like -OH or -NH2.

	//Case D) Interconversion rate constants $k_{AB}$ and $k_{BA}$ are very quick compared to the intrinsic lifetimes $\tau_A$ and $\tau_B$.// In this case the equations of case C would still apply. But in practice, a quick equilibrium between reactants and product would be established. This means that the concentrations of A and B with respect to each other would always be constant prior to their decay, and hence the whole system could be treated as a single dye. The decay would be single exponential, being an average of $\tau_A$ and $\tau_B$ weighted by their fraction in the equilibrium.		//Case D) Interconversion rate constants $k_{AB}$ and $k_{BA}$ are very quick compared to the intrinsic lifetimes $\tau_A$ and $\tau_B$.// In this case the equations of case C would still apply. But in practice, a quick equilibrium between reactants and product would be established. This means that the concentrations of A and B with respect to each other would always be constant prior to their decay, and hence the whole system could be treated as a single dye. The decay would be single exponential, being an average of $\tau_A$ and $\tau_B$ weighted by their fraction in the equilibrium.

-	This situation may happen if compounds A and X were directly in contact prior to excitation, for example throgh ground-state interactions.	+	This situation may happen if compounds A and X were directly in contact prior to excitation, for example through ground-state interactions.
	===== 3) Solvation dynamics =====		===== 3) Solvation dynamics =====


-	Even pure fluorophores in pure solvents may lead to multiexponential decays. This is the case of molecules with strong charge transfer character in polar solvents when undergoing solvation dynamics. In such cases the fluorescence spectra shifts to longer wavelengths in time. Measuring the decay in the blue edge of the steady-state spectrum will lead to a multiexponential decay. The ns lifetimes corresponds to the intrinsic fluorescence lifetime of the fluorophore, whereas the ultrafast components (ps) are related to the rate of the shift. Measuring in the red-flank of the steady-sate spectrum leads to multiexponential decays with positive (intrinsic lifetime, ns) an negative (rate of shift, ps) pre-exponential factors. This is depicted in Scheme 3.	+	Even pure fluorophores in pure solvents may lead to multiexponential decays. This is the case of molecules with strong charge transfer character in polar solvents when undergoing solvation dynamics. In such cases the fluorescence spectrum shifts to longer wavelengths on a picosecond time-scale. Measuring the decay in the blue edge of the steady-state spectrum will lead to a multiexponential decay. The ns lifetime corresponds to the intrinsic fluorescence lifetime of the fluorophore, whereas the ultrafast components (ps) are related to the rate of the shift. Measuring in the red-flank of the steady-sate spectrum leads to multiexponential decays with positive (intrinsic lifetime, ns) and negative (rate of shift, ps) pre-exponential factors. This is depicted in Scheme 3.


	{{:solvation_dynamics.png?800\|}}		{{:solvation_dynamics.png?800\|}}

-	Scheme 3. Left: energetic representation of solvation dynamics. The fluorophore is represented as a sphere with a pointing dipole. Solvent molecules are represented in gray around the fluorophore. Right up : Spectral consequence of solvation dynamics. The fluorescence spectrum shifts in time to lower energies. Right bottom: Decay traces measured in different spectral regions. Blue flanks are multiexponential with positive pre-exponentila factors, red flanks are multiexponential with rising components.	+	Scheme 3. Left : energetic representation of solvation dynamics. The fluorophore is represented as a sphere with a pointing dipole. Solvent molecules are represented in gray around the fluorophore. Right, top : Spectral consequence of solvation dynamics. The fluorescence spectrum shifts in time to lower energies. Right, bottom: Decay traces measured in different spectral regions. Blue curves are multiexponential with positive pre-exponentila factors, red curves are multiexponential with rising components.

-	Before the excitation, the fluorophore is in the ground state S0 , which has a characteristic dipole moment. Solvent molecules, which also have their characteristic dipole moment are oriented in such a way that the interactions dipole-dipole with the fluorophore are as favorable possible. When the fluorophore is prompted to the excited state, its electronic distribution switches almost instantly. At time zero after excitation the solvent molecules remain in their "original" orientation to solvate ground state . The resulting dipole -dipole interactions with the fluorophore are hence less favorable. As a result , the solvent begins to relax to solvate the S1 state and brings the system to a more favorable position. Spectroscopically, this is manifested by the time-shift of the emission spectrum to longer wavelengths. Consider that the Steady-State spectrum is the time integral of all those shifting spectra. Measuring in the blue flank (λ1) will lead to a multiexponential decay: the signal decreases because of the shift and the intrinsic decay. Measuring in the red flank (λ3) will lead to a multiexponential decay with a negative pre-exponential factor: the signal first rises due to the increase in signal due to the displacement, and then decays due to the fluorescence lifetime.	+	Before the excitation, the fluorophore is in the ground state S0 , which has a characteristic dipole moment. Solvent molecules, which also have their characteristic dipole moment are oriented in such a way that the dipole-dipole interactions with the fluorophore are as favorable as possible. When the fluorophore is prompted to the excited state, its electronic distribution switches almost instantly. At time zero after excitation the solvent molecules remain in their "original" orientation. The resulting dipole -dipole interactions with the fluorophore are hence less favorable. As a result, the solvent begins to relax to solvate the S1 state and brings the system to a more favorable position. Spectroscopically, this is manifested by the time-shift of the emission spectrum to longer wavelengths. Consider that the Steady-State spectrum is the time integral of all those shifting spectra. Measuring in the blue flank (λ1) will lead to a multiexponential decay: the signal decreases because of the shift and the intrinsic decay. Measuring in the red flank (λ3) will lead to a multiexponential decay with a negative pre-exponential factor: the signal first rises due to the increase in signal due to the displacement, and then decays due to the fluorescence lifetime.

	In fluid media, solvation dynamics can be described with a multiexponential function spanning from the femtosecond time-scale to tens of picoseconds. Hence, the tail of this process can be monitored with a TCSPC spectrometer equipped with fast detectors such as a [[glossary:MCP]] or a Hybrid-PMT. In viscous media or at low temperatures, the ps tail component slows down to ns, and the process can be monitored with slower detectors, such as standard [[glossary:PMT]].		In fluid media, solvation dynamics can be described with a multiexponential function spanning from the femtosecond time-scale to tens of picoseconds. Hence, the tail of this process can be monitored with a TCSPC spectrometer equipped with fast detectors such as a [[glossary:MCP]] or a Hybrid-PMT. In viscous media or at low temperatures, the ps tail component slows down to ns, and the process can be monitored with slower detectors, such as standard [[glossary:PMT]].