"Diffraction by helical structures"

Date:
1956-1957
Reference:
PP/CRI/H/2/17
Catalogue details

Licence: In copyright

Credit: "Diffraction by helical structures". Source: Wellcome Collection.

    20/98
    accessible structure factor^ terms G (R) 9 or at least of some of them f and we wish to use the® with the observed moduli calulate the electron density, it will be convenient to work not with a group of atoms but in O- CO*t\«woOS terms of distribution of electron density f(r, t z) f Then expression (1) for the structure factor on a layer line in l&o c«#e where only «ne-B CHIMI function term- need W considered - F(M,V) =- ^{jçO,V) X k IJMÍ) [*(*+£) -yxV+Air^J ¿T \ r „ (¡3) where now ~ Jjï e (*A l ) J« (¿rt <«■) «^. [i (-1V + afrf* low since the electron density ^ is periodic in Tand in z we may expand it in the form of a double Fourier series ç(*;V) = %,< (O ty[ -<*> -fft where the j ^(ij are in general complex functions of f° * The Fourier transform of this will be given by - (ft ç(r,(f,i)t*ffiircf/lran>(<f y Y¿|] (I r Substituting from (1?) we find t as we expect th&t the Integral over z will be non-zero only when ^ ~ ^ l*e< that the scattering is confined to layer-planes# On any one layer-plane *t we then have flM, k) ^ Ii «bit**) UAr<nl<r-Y)]4trlnr OÍZ-