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  1. #1

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    2 electron sensitization & latent image questions

    I'm making my way through Haist right now and I think I've read enough to actually formulate a question now. Haha. Is two electron sensitization a process by where you can make a latent image site with two as opposed to three photoelectrons? Or is it something else? Am I right in saying that to make a development site, you need at least three photons?

    I find it fascinating that film was/is such a huge industry and yet we don't actually know the mechanics of how the latent image is actually formed. Has more work been done in this area that postdates Haist? Or is it still up in the air? I guess if we don't know exactly how it works by now, we probably never will, given the decline of film.

  2. #2
    Photo Engineer's Avatar
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    Basically, you are correct. Also, the method was unknown at the time the books (Haist) were written. It uses a penta cyano osmate complex with a dye to achieve this.

    And no, no one will ever know the full story AFAIK. We are watching a tragedy unfold and most people do not care.

    PE

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    Thanks about the 2 electron business. I used to think we were going from 1 -> 2, not 3 -> 2. I guess I was thinking that effective speed was doubled, so electron sensitization doubled. haha.

    That irks me about the latent image thing. If it I grew up 40 years ago, I think I would have been tried to do research in photo. I feel like I've arrived to the party late.

  4. #4
    AgX
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    Tim,

    things are even more complex: gaining a stable nucleus does not necessarily mean that is developable.

    Those last concepts in enhancing sensitivity were all based on scavenging a hole while at the same time yielding a 2nd electron (next to that photolytic one) from a coupled reaction.
    Concepts varied in efficiency and practicability.

    Anyway, they relate to the efficiency by which use is made of an absorbed photon, not to the number of electrons needed for a nucleus.
    Last edited by AgX; 02-06-2009 at 10:04 PM. Click to view previous post history.

  5. #5
    keithwms's Avatar
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    Quote Originally Posted by Tim Gray View Post
    That irks me about the latent image thing. If it I grew up 40 years ago, I think I would have been tried to do research in photo. I feel like I've arrived to the party late.
    Before he passed, I got to know Jack Mitchell (just look up "latent image" in wikipedia) and he was really upset at how quickly the research stagnated. He expressed extreme dismay with Kodak and told me that if I wanted to carry on with his work I should move to Japan. Very irritated, Jack was! I later realized that he'd had some sort of bashing of heads with someone at Kodak (I don't recall the name) on the subject of alternative sensitization schemes. According to Jack, there was/is all sorts of room for improvement, but the research was simply stopped. The only thing that put a smile on his face was that I told him I was still happily using panatomic-x!

    Jack had late-stage Alzheimer's, and our discussions were extremely scattered, so I had trouble piecing his stories together with concrete dates, but my general impression was that according to him, circa 1990, research at Kodak began to stumble and there was no real interest there in "saving" film at the highest levels of the company.
    "Only dead fish follow the stream"

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    Quote Originally Posted by Photo Engineer View Post
    Basically, you are correct. Also, the method was unknown at the time the books (Haist) were written. It uses a penta cyano osmate complex with a dye to achieve this.

    And no, no one will ever know the full story AFAIK. We are watching a tragedy unfold and most people do not care.

    PE

    Wow! I had no idea that this process is still largely an unknown quantity. I guess only quantum electrochemistry has a chance at answering the question of what exactly happens when light hits film, right?

  7. #7
    AgX
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    We ain't know nothing yet.

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    I would love to do research in this, but it's a bit outside my field. Probably be hard to get grant money too.

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    keithwms's Avatar
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    B&Wpositive, according to Jack, there was a lot of solid-state physics involved. Of course, one has to consider grain geometry and the placement of sensitizers along the grains etc. And the basic picture you can have in your head is that a photon comes in, generates an exciton (electron-hole pair). The electron goes off and does its thing. But in nanoparticles there is extremely strong exciton binding energy and what the hole does most certainly does affect what the electron does. Their migration is likely correlated, so... Jack's big contribution was basically "don't forget the hole!" And I suppose he had the idea that you want to prevent recombination of the electron and hole. That's my 30 sec explanation

    And yes, Tim, it is very hard to get grant money for this especially now. But I gathered form Jack that even in "the day" money was not plentiful and he got money from his father to support much of his work. His father got money from the bright idea of using a camera to reproduce maps, rather than redrawing them by hand.
    "Only dead fish follow the stream"

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    Haha. Well in that case I'll stick to the DOE and NSF

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