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Quite so. But in this case he's not looking for an antistokes shift  
just re-emission of the same apparent energy. It's the lower  
probability of re-emission at this wavelength that prevents violation  
of the second law.

Cheers

On 28/04/2011, at 10:30 PM, Andreas Bruckbauer wrote:

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>
>
> To distinguish between Rayleigh or Mie scattering ('reflection') and  
> photoluminescence you would need to measure time resolved, see e.g.  
> G. Plesson et al. PHYSICAL REVIEW B 70, 205424 (2004). What you  
> measure is most likely the excitation light, but you could try to  
> vary the with of the excitation line if this is possible in your  
> instrument and see if the peak varies accordingly.
>
> I think what Mark meant was the interaction of the excited electron  
> with phonons, usually the energy is dissipated as phonons but you  
> could also have phonons transferring energy to the electron in which  
> case it would gain energy from the phonon. If it does not relax  
> further and goes back into the ground state by emitting a photon,  
> you will get anti stokes fluorescence. At room temperature the  
> energy of a single phonon would be around kT (25 meV compared to 3  
> eV for a blue photon), so you need a lot of electron-phonon  
> interaction to make a noticable shift.
>
> In case of the metal particle you will also have plasmon excitation.
>
> best wishes
>
> Andreas
>
>
>
>
>
>
> -----Original Message-----
> From: Johannes-P. Koch <[log in to unmask]>
> To: [log in to unmask]
> Sent: Thu, 28 Apr 2011 8:27
> Subject: Re: same excitation and emission peaks
>
>
> *****
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>
> Think so too; if you measure something in a fluorimeter, you always  
> get a scattering "line" or peak (if looking at your spectra in 2D)!
>
>
> Mark, could you comment on your phonon stuff?
>
> To my knowledge, phonons as such do not fluoresce; they do interact  
> with photons, i.e. you can generate a fluorescing photon by  
> annihilating a phonon or vice versa; still wherever you go, their is  
> some loss of energy, meaning that you cannot have exactly the same  
> peaks. - probabilistic or not!
>
> Johannes
>
> Am 28.04.2011 08:57, schrieb Sudipta Maiti:
>> *****
>> To join, leave or search the confocal microscopy listserv, go to:
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>>
>> are you not just looking at Rayleigh scattering?
>> Sudipta
>> On Thu, 28 Apr 2011 12:24:29 +0530, charu tanwar wrote
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>>> To join, leave or search the confocal microscopy listserv, go to:
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>>>
>>> yes...that is what i also thought of. But this is the data we are
>>> getting after repeatedly doing the experiment. Thanks
>>>
>>> CHARU TANWAR
>>> Imaging Specialist
>>> Advanced Instrumentation Research Facility
>>> Jawaharlal Nehru University
>>> New Delhi 110067
>>> India.
>>>
>>> --- On Wed, 27/4/11, Jeffrey L. Travis<[log in to unmask]>  wrote:
>>>
>>> From: Jeffrey L. Travis<[log in to unmask]>
>>> Subject: Re: same excitation and emission peaks
>>> To: [log in to unmask]
>>> Date: Wednesday, 27 April, 2011, 7:33 PM
>>>
>>> *****
>>> To join, leave or search the confocal microscopy listserv, go to:
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>>> Wouldn't that violate the Second Law?
>>>
>>> On 4/27/2011 9:59 AM, Charu Tanwar wrote:
>>>> *****
>>>> To join, leave or search the confocal microscopy listserv, go to:
>>>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
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>>>>
>>>> Dear List
>>>>
>>>> Not a direct confocal related query.
>>>> Anyone please let me know whether any metallic nanoparticle with a
>> definite size
>>>> can have the same emission peak as its excitation peak???
>>>>
>>>> Thanks in advance
>>>>
>>>> Charu Tanwar
>>>> Imaging Specialist
>>>> Advanced Instrumentation Research Facility
>>>> Jawaharlal Nehru University
>>>> New Delhi
>>>> India.
>>>>
>>>>
>>
>>
>> Dr. Sudipta Maiti
>> Associate Professor
>> Dept. of Chemical Sciences
>> Tata Institute of Fundamental Research
>> Homi Bhabha Raod, Colaba, Mumbai 400005
>> Ph. 91-22-2278-2716 / 2539
>> Fax: 91-22-2280-4610
>> alternate e-mail: [log in to unmask]
>> url: biophotonics.wetpaint.com
>>
>
> -- Mag. Johannes-P. KOCH 
> Department of Biochemistry and Cell Biology
> MFPL, University of Vienna
> Dr. Bohrgasse 9/5
> A-1030 Vienna
> Austria
>
> phone: 0043 1 4277 52809
> fax: 0043 1 4277 9528
>
> mail to: [log in to unmask]
>
>
>