Talk:Magnetic circular dichroism

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This article was automatically assessed because at least one WikiProject had rated the article as stub, and the rating on other projects was brought up to Stub class. BetacommandBot 09:59, 10 November 2007 (UTC)

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In this section there is the statement "In the case of ferric hemoproteins, MCD is capable of determining both oxidation and spin state to a remarkably exquisite degree." Ferric implies Fe(III). Should this statement simply read: "In the case of hemoproteins...", or is the sentence supposed to mean that if the iron is Fe(III) in the proteins resting state that MCD has these capabilities? BobertWABC (talk) 22:50, 4 March 2008 (UTC)

optical schematic

A suggestion for improving this useful schematic. I think it is helpful to show that the lock in amplifier gets its reference signal from the photoelastic modulator.

I think the extraordinary pmt, as shown in the diagram, contrary to statements in the article, can measure source intensity changes but can not measure, by itself, the effects of sample absorbance. I think the ratio of the average signal in the sample pmt to the signal in the extraordinary pmt will change as sample absorbance changes. This average signal (called V_dc in the article) must be measured separately from the lock in amplifier. It would improve the explanatory power of the diagram to show this additional signal path.

In MCD systems I am familiar with, sample absorbance effects are controlled with a single pmt, by doubly modulating the light beam by adding an optical chopper, before the monochromator if possible, and using a second lock in amplifier synchronized to the chopper to measure average changes in intensity of light passing through the sample to the same sample pmt. If the light is chopped before entering the monochromator, then it is possible to discriminate against stray light from the monochromator, which can be high in the near infrared, and which might distort the absorbance measurements otherwise.

There are various ways to use this information. One way is to vary the pmt gain to keep this average signal constant, thereby making the MCD signal amplitude independent of sample absorbance. This takes advantage of the pmt as a high dynamic range, low noise amplifier to improve the dynamic range of the instrument. If the instrument described in the diagram uses this approach, which it might, this pmt gain control signal path could be shown as well.

--AJim (talk) 21:59, 21 April 2010 (UTC)

Basic terms

There should be a line or two of more basic explanation in the opening paragraph. Before launching into explanations that require a dictionary pitstop every 10-20 words. Is that too much to ask? — Preceding unsigned comment added by 165.228.63.179 (talk) 02:26, 4 June 2013 (UTC)