Tomas,
I would be very surprised if pure H2O ice would have a negative
correlation of RI and T. However, ice with nanopores and perhaps
amorphous ice forming directly from vapor may have variable and
anomalous optical properties. Annealed ice would then change to
approach pure H2O. Is your window near a roadway? A lot of salt dust
is kicked up along roads and it could further change the optics. You
should e-mail Barclay Kamb (prof. emeritus at CalTech). He made a lot
of optical observations on ice.
cheers,
eric
Quoting Tomas Feininger <[log in to unmask]>:
>
> 6.i.'09
>
> Hello fellow Toilers,
>
> I live in a cold climate. Air temperatures less than -15 C
> are common from early December through March. At times the
> temperature even dips below -30 C. Simple observation of ice
> crystals on the inside surface of exterior window panes (double or
> triple glazing, so the crystals are at or close to the outside air
> temperature) leads me to believe that the optical properties of ice
> are temperature-dependent. Namely, the refractive indices and
> dispersion of ice appear to be inversely proportional to T. Is this
> real, or am I fooling myself? Can someone throw light (not heat!)
> on the subject? Thank you,
>
> Tomas Feininger Professeur de géologie Université Laval Québec
>
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