[phenixbb] scattering factors
Goragot Wisedchaisri
goragot at u.washington.edu
Mon Jun 20 13:45:28 PDT 2011
Hi Ralf,
No, the factor m/m0 is independent of atom types for the same acceleration voltage (m0 is electron rest mass, m is relativistic mass of electron which depends on acceleration voltage. The Guassian ai and bi coefficients already take care of fitting scattering factor f(e) for each atom type. In another word, if you can implement a function that calculates and multiplies m/m0 to all the ai coefficients for all atom types in the table, users will only need to input the acceleration voltage.
Thanks,
George Wisedchaisri
On Mon, 20 Jun 2011, Ralf Grosse-Kunstleve wrote:
> Hi George,
>
>> I have a question though. Because electron scattering depends on the
>> velocity of the electron which in turn depends on the acceleration voltage
>> of the microscope. The gaussian parameters need to be corrected using the
>> relativistic electron velocity by multiplying the ai parameters with m/m0 =
>> (1 – v2/c2) ^-1/2 where v is the relativistic electron velocity and c is the
>> velocity of light (for example m/m0 = 1.58707 for a 300keV electron
>> microscope).
>
> Is the factor m/m0 different for each atom type?
>
> Ralf
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