The count rate becomes linearly pro

The count rate becomes linearly proportional to the atomic-density of
the element of interest, for a given sample thickness. Also, since
is evaluated for the element of interest, then as Eq. (8.15) indicates,
the count rate is also independent of the composition of the
sample, that is independent of the presence of other elements, since the
total cross-sections and do not appear in the measurement model.
For larger values of as Eq. (8.14) indicates, the count rate
becomes nonlinearly dependent on since the value of also affects
the value of and However, for very large values of
the exponential term in Eq. (8.14) becomes negligible and the count rate
reaches a saturation value, of:
This saturation value is the maximum count rate obtainable, and the
thickness at which this value is reached is known
or the “infinite thickness”. Then, the count rate, though independent
as the critical thickness
of the thickness, is influenced by the composition and density of the
object, due to the presence of and in Eq. (8.16). If one considers
the critical thickness to be attained at a value of equal to, say,
six, with then the critical thickness can taken as
equal to This is still a small value for most materials, given the
low energy of the photon source needed to cause excitation. Therefore,
even for a large sample, only a skin-deep layer, about in thickness,
on the surface of the source is analyzed, by monitoring emissions from
near the surface.
The model of Eq. (8.12) does not include the effect of Compton scattering,
which competes with the photoelectric-effect as explained in section
3.4. Since the photon energy of the excitation source has to be
slightly higher than the binding energy of the electrons in the K shells
of the atom, Compton scattering can reduce the energy of the incident
photons, according to Eq. (3.37), to values equal or below the required
excitation-energy. The scattered photons can also reach the detector
measuring the XRF emissions. The detected photons at the energy of
interest will then contain an XRF component, and a background component
from Compton scattering. However, by proper design of the setup,
Comptori-scattered photons can be made to scatter at a large angle, so
that their energy is well below the monitored XRF photon energy.
Self-excitation is another complicating factor that is not considered
in the model of Eq. (8.12). The emitted XRF photons resulting from one
element can themselves be absorbed by other elements within the object,
causing excitation of one or more of these elements in the sample. For

Kết quả (Việt) 1:

The count rate becomes linearly proportional to the atomic-density ofthe element of interest, for a given sample thickness. Also, sinceis evaluated for the element of interest, then as Eq. (8.15) indicates,the count rate is also independent of the composition of thesample, that is independent of the presence of other elements, since thetotal cross-sections and do not appear in the measurement model.For larger values of as Eq. (8.14) indicates, the count ratebecomes nonlinearly dependent on since the value of also affectsthe value of and However, for very large values ofthe exponential term in Eq. (8.14) becomes negligible and the count ratereaches a saturation value, of:This saturation value is the maximum count rate obtainable, and thethickness at which this value is reached is knownor the “infinite thickness”. Then, the count rate, though independentas the critical thicknessof the thickness, is influenced by the composition and density of theobject, due to the presence of and in Eq. (8.16). If one considersthe critical thickness to be attained at a value of equal to, say,six, with then the critical thickness can taken asequal to This is still a small value for most materials, given thelow energy of the photon source needed to cause excitation. Therefore,even for a large sample, only a skin-deep layer, about in thickness,on the surface of the source is analyzed, by monitoring emissions fromgần bề mặt.Các mô hình của Eq. (8,12) không bao gồm các hiệu ứng của Compton phân tán,mà cạnh tranh với các hiệu ứng quang điện, như được diễn tả trong phần3.4. kể từ khi năng lượng photon của kích thích nguồn đãhơi cao hơn năng lượng ràng buộc của các điện tử trong vỏ Knguyên tử, Compton tán xạ có thể làm giảm năng lượng của sự kiệnphoton, theo Eq. (3.37), giá trị bằng hoặc dưới các yêu cầukích thích-năng lượng. Photon rải rác cũng có thể tiếp cận các máy dòđo lượng phát thải XRF. Các photon được phát hiện tại năng lượng củaquan tâm sau đó sẽ chứa một thành phần XRF và một thành phần nềntừ Compton tán xạ. Tuy nhiên, bởi các thiết kế phù hợp của các thiết lập,Comptori rải rác photon có thể được thực hiện để phân tán ở một góc độ lớn, vì vậyrằng năng lượng của họ là thấp năng lượng photon XRF giám sát.Tự kích thích là một yếu tố phức tạp mà không được coi làtrong mô hình Eq. (8,12). Các photon XRF phát ra từ mộtyếu tố có thể mình được hấp thụ bởi các yếu tố khác trong đối tượng,gây ra kích thích của một hoặc nhiều của các yếu tố trong mẫu. Cho