and M main levels can be approximat

and M main levels can be approximately expressed as [267]:
The K and L x-rays are the most distinguishable x-rays, due to the
large energy difference between these two levels and the energy levels of
outer electron orbits. Table 8.13 lists the energy of the emissions
from some atoms. Since the energy levels of an atom depends on its
atomic number, the emitted x-rays are characteristic of the atom, and
can be detected and used for elemental identification. Si(Li) detectors,
see section 4.3.3, are usually used for detecting these low-energy photons.
However, Si (Li) detectors are sensitive to photons of energy below
30 keV, or so. Therefore, they can detect K x-ray emissions from elements
of atomic-number, Z, from 11 (Na) to 55 (Cs), but are insensitive
to K x-rays generated from elements of Z from 70 (Yb) to 82 (Pb).
However, L x-rays of these heavier elements are detectable by a Si(Li)
detector. Elements of Z between 56 (Ba) and 69 (Tm) are difficult to
analyze with a Si(Li) detector, since their K x-ray emissions are above
the upper energy limit of the detector, while they produce L x-rays with
energies that overlap with the K x-rays of lighter elements. However,
planar high purity germanium (HPGe) detectors, see section 4.3.3, are
sensitive to photons in the 30 to 125 keV range. This allows the detection
of the K x-rays of many elements. Since chemical bonds occur
mainly between electrons in the outer shell of the atom, emissions from
the inner K and L shells are not affected greatly by chemical bonds, except
for light elements. The following sections discuss the three different
methods used for generating XRF by atomic excitation.
Excitation by Isotopic Sources
Isotopic sources can be used for atomic excitation, if they produce
photons with energies that are as close as possible (but higher than) the
binding energies of the K or L shells of the atoms of interest. Table 8.14
lists some radioisotopic sources and the elements they can excite.
As Table 8.14 indicates, the source energy used in XRF is quite low
for most elements, since the electron binding energy is generally low, as
indicated by the energies of the elements listed Table 8.13. These low
excitation energies introduce a number of factors that should be taken
into account when arriving at a measurement model for XRF. First, as

Kết quả (Việt) 1:

and M main levels can be approximately expressed as [267]:The K and L x-rays are the most distinguishable x-rays, due to thelarge energy difference between these two levels and the energy levels ofouter electron orbits. Table 8.13 lists the energy of the emissionsfrom some atoms. Since the energy levels of an atom depends on itsatomic number, the emitted x-rays are characteristic of the atom, andcan be detected and used for elemental identification. Si(Li) detectors,see section 4.3.3, are usually used for detecting these low-energy photons.However, Si (Li) detectors are sensitive to photons of energy below30 keV, or so. Therefore, they can detect K x-ray emissions from elementsof atomic-number, Z, from 11 (Na) to 55 (Cs), but are insensitiveto K x-rays generated from elements of Z from 70 (Yb) to 82 (Pb).However, L x-rays of these heavier elements are detectable by a Si(Li)detector. Elements of Z between 56 (Ba) and 69 (Tm) are difficult toanalyze with a Si(Li) detector, since their K x-ray emissions are abovethe upper energy limit of the detector, while they produce L x-rays withenergies that overlap with the K x-rays of lighter elements. However,planar high purity germanium (HPGe) detectors, see section 4.3.3, aresensitive to photons in the 30 to 125 keV range. This allows the detectionof the K x-rays of many elements. Since chemical bonds occurmainly between electrons in the outer shell of the atom, emissions fromK và L bên trong vỏ không ảnh hưởng rất nhiều bởi các liên kết hóa học, ngoại trừcho các phần tử ánh sáng. Phần sau đây thảo luận về ba khác nhauphương pháp được sử dụng để tạo ra XRF bởi nguyên tử kích thích.Kích thích bởi các đồng vị nguồnĐồng vị nguồn có thể được sử dụng cho nguyên tử kích thích, nếu họ sản xuấtphoton với năng lượng đó là càng gần càng tốt (nhưng cao hơn) cácràng buộc các năng lượng của các lớp vỏ K hoặc L của các nguyên tử của lãi suất. Bảng 8.14liệt kê một số nguồn radioisotopic và các yếu tố mà họ có thể kích thích.Như bảng 8.14 ngụ ý, nguồn năng lượng được sử dụng trong XRF là khá thấpĐối với hầu hết các thành phần, kể từ electron ràng buộc năng lượng là nói chung thấp, nhưđược chỉ định bởi các nguồn năng lượng của các yếu tố liệt kê bảng 8.13. Những thấpnăng lượng kích thích giới thiệu một số yếu tố cần được thực hiệnvào tài khoản khi đến một mô hình đo lường cho XRF. Đầu tiên, như