k-shell jump ratios and jump factors for platinum and lead

7/22/2019 K-SHELL JUMP RATIOS AND JUMP FACTORS FOR PLATINUM AND LEAD

1/5

MEASUREMENT OF K-SHELL JUMP RATIOS AND JUMP FACTORS

FOR PLATINUM AND LEAD BY USING 2-GEOMETRICAL

CONFIGURATION AND A WEAK GAMMA SOURCE

L. Francis Maria Anand, S. B. Gudennavar*

and S. G. Bubbly

Department of Physics, Christ University, Bangalore-560 029, Karantaka.

* Correspondence: [email protected]

Abstract - ISBN 978-93-81104-23-1 NSNMRN-2012 (SEP 12-14) -

OOTY

The article presents a simple method of measuring K- shell absorption jump ratios and jump factors for elementsand compounds in the field of x-ray spectroscopy. The K- shell jump ratios and jump factors for Platinum and

Lead are measured by adopting 2-geometrical configuration and a weak gamma source. The K x-ray photonsare excited in the targets using 123.6 keV weighted average energy gamma photons from a weak 57Co

radioactive source and the fluorescent K x-ray photons are detected using low energy HPGe x-ray detector

coupled to a 16k multichannel analyser. The total atomic attenuation cross section for the elements is measuredexperimentally from the incident and the transmitted spectra whereas the K x-ray intensity ratios from x-ray

fluorescent spectrum. The total atomic scattering cross sections are calculated using WinXcom software. The K-

shell jump factor and jump ratio are computed using the measured K x-ray intensity ratios and total atomicattenuation cross section, and the calculated K x-ray production cross section and total atomic scattering cross

sections. The computed values of K- shell jump factor and jump ratio for platinum and lead are compared withthe theoretical values and others experimental data, and we found a good agreement between them. Thus, from

the present study we conclude that our 2- geometrical configuration method with weak gamma source can be analternative simple method to measure various atomic parameters in the field of x-ray spectroscopy.

Keywords:2-geometrical configuration, total atomic absorption cross section, intensity ratios, jump ratio, jump factor.

1. Introduction

K x-ray intensity ratios, the K-shellabsorption jump factors and rK, jump ratios

are of great significance in the field of

interaction of gamma-rays and x-rays with

matter [1]. They too find applications in

the other areas such as medical physics

and material science [2]. Several

researchers have adopted various methods

to measure these parameters, namely; the

gamma ray attenuation method [3], the

Compton peak attenuation method [4-6],

the energy dispersive x-ray fluorescencemethod (EDXRF) [7-9] and the

bremsstrahlung transmission method [10].

These methods have their own advantages

and disadvantages. For example, the

gamma ray attenuation method requires

many monoenergetic gamma sources and

thin foils of given element, while the

EDXRF method requires strong

radioactive sources of the order 100mCi or

more. For details refer the research article

by Bennal and Badiger [1]. In the presentwork, we measure these parameters for

platinum and lead using a simple method

proposed by Gudennavar et al. [11] to

measure K x-ray fluorescence parameters,which employs a weak gamma source and

a 2-geometrical configuration.

2. Theory

The total atomic attenuation cross section

for gamma photons in a material target of

thickness t is given by

(1)where A is the atomic weight of the target

element, N0 is the Avogadro number, I0 is

intensity of incident gamma photons and Itis the transmitted intensity. The plot of tversus photon energy gives a saw-tooth

curve around the binding energy of the K-

shell of the target atom, which has three

regions: a lower energy branch, a sudden

increase in the K-shell binding energy and

an upper energy branch. The lower energy

branch corresponds to the total atomic

photoelectric cross section due to L-, M-

1


2/5

and higher shells. The upper energy branch

corresponds to the total atomic

photoelectric cross section due to K-, L-,

M- and higher shells. The sudden rise is

essentially due to the onset of the K-shell

photoelectric cross section. The ratio of theabsorption cross section at the upper

energy branch and that at lower energy

branch gives the K-shell jump ratio, rK, and

is given by [12]

(2)

where t is the total absorption cross

section and K, L, M are the photoelectric

absorption cross sections for the K-, L-,M-shells respectively.

The K-shell absorption jump factor, JK, is

related to the K-shell jump ratio, rK, and is

defined as the probability that an electron

is ejected from the of K-shell of the target

element other than any other shells,

(3)

It must be noted that the jump factors, JK,

can also be determined if we measure the

K x-ray parameters such as K x-ray

fluorescence yield, K x-ray production

cross section and K to K x-ray intensity

ratio using the relation [7],

(4)

where K is K x-ray production cross

section, t is the total atomic attenuationcross section, ts is the (coherent +

incoherent) atomic scattering cross section,

IK/IK is the intensity ratio of the K and

K x-rays at photon energy E and K is the

K-shell fluorescence yield of the target

atom.

The K x-ray intensity ratios are the ratios

of the intensities of K to K. The ratio of

the intensity of the characteristic x-ray of

type i to type j is given by

(5)

where i = K and j = K, and are the

measured K x-ray intensities of type i and j

respectively, i and j are the efficiencies

of the detector for the K x-ray of type i and

j respectively, i and j are the self-

absorption correction factors for the K x-

ray of type i and type j respectively in the

target material and are calculated using the

eqn. (6), exp(-xiwtw) and exp(-xjwtw) are

the window attenuation correction factors

for the K x-ray of type i and j respectively;

here xiw and xjw are the mass attenuation

coefficients for the K x-ray of type i and jin the detector window of thickness tw.

Taking into account the isotropic emission

of K x-rays and the fact that we are

measuring the intensity of x-ray photons

emerging from the target in all the forward

directions, that is, emitting into a solid

angle of 2 sr., we use the correction

factor without involving the scattering

angles:

)t())texp(-(-1

ei

ei

+

+= (6)

where i and e are the mass attenuation

coefficients of the incident and emitted K

x-ray photons respectively in the target and

are computed using WinXcom software

[13].

The total number of K x-ray photons of

given type (i = K and K) emitted from

the target in all directions is given by

)texp(

I2I

wxwx

'

i

i

= (7)

where'

iI is the measured intensity of K x-

ray of type i.

3. Experimental

The Experimental setup adopted in the

present investigation is shown in Fig. 1.

The gamma photons of energy 123.6 keV,

i.e. the weighted average of 122 and 136keV, from 57Co source (~104 Bq) are used

2


3/5

to produce the K x-rays in the target and

these x-rays are detected with a HPGe

detector (active area 500 mm2, 10 mm

thickness, Be window of thickness 0.6

mm) connected to a DSA-1000 (a built-in

amplifier and 16k MCA). The energyresolution of the detector is 200 eV at 5.9

keV and the efficiency is nearly 100% for

3-500 keV. The spectrometer is calibrated

using various gamma sources. The target

materials are pure elements procured in the

form of thin foils from Alfa Aesar A

Johnson Matthey Company UK.

Fig. 1. Experimental arrangement.

3.1 Measurement of total atomic

attenuation cross section

The incident source spectrum (source plus

background spectrum) was acquired for

2400s by placing just the weak57Co source

on the window of the detector. The

intensity of 122 and 136 keV was carefully

estimated from the background corrected

source spectrum (Fig. 2) and the two

together give I0. Now by sandwiching the

respective target between the source and

the detectors window, the transmittedspectrum (transmitted spectrum plus

background) is obtained for the same

interval of time (Fig. 3). The transmitted

intensity It is estimated for the same 122

and 136 keV photons from the the

transmitted spectrum. Knowing I0 and It,

the total atomic attenuation cross section tfor gamma photons of energy 123.6 keV in

a target of thickness t is calculated using

eqn. (1). The total atomic scattering cross

section t is calculated using WinXcomsoftware [13].

3.2 Measurement of K x-ray intensities

By subtracting the source spectrum plus

background from the transmitted

Fig. 2. Source plus background spectrum

Fig. 3. Transmitted spectrum plus

background

spectrum plus background, we get a clean

fluorescence K x-ray spectrum that

corresponds to the target element under

investigation. The K x-ray fluorescence

spectrum for platinum is shown in Fig. 4.

The area under each peak gives'

iI , the

measured intensity of K x-ray of type i

(where i = K and K); which is corrected

for self-attenuation in the target ( factor),

attenuation in the window and efficiency

of the detector.

The K x-ray production cross section for a

given element is calculated using the

relation,

(8)

where fK is the fractional emission rate

and is given as, fK = (1+IK/IK)

-1

. The Kvalues are taken from Hubbell [14] and K

3


4/5

values at 123.6 keV are taken from

Scofield [15].

Fig. 4. K x-ray fluorescence spectrum of

platinum

4. Results, Discussion and conclusions

The measured values of K x-ray intensity

ratios, K shell jump ratios and jump

factors determined for platinum and lead

are presented in Table 1. These values are

compared with the theoretical and others

experimental values in the same table.

Table 1. Measured values of K x-ray

intensity ratios, jump ratios and jump

factors for platinum and lead

K XRF

Parameters

Platinum

(Z = 78)

Lead

(Z = 82)

K 0.9593 [14] 0.9634 [14]

t (Exptl.) 991 1138

t (Theor) 964 [16] 1120 [16]

K using

eqn (8)

527.68 621.02

IK/IK(Exptl)

0.2700.005 0.2800.002

IK/IK(Theor)

0.263 [15] 0.270 [15]

IK/IK(Others

values) 0.259 [18]

0.28220.007

[19]

0.2750.021

[20]

rK(Exptl.) 4.24 4.61

rK(Theor) 4.95 [16] 4.74 [16]

rK(Others

values)

4.63 [17] 5.11 [17]

JK(Exptl.) 0.764 0.778

JK(Theor) 0.798 [16] 0.789 [16]JK(Others 0.784 [17] 0.804 [17]

values)

From the table, we see that the measured

values of K x-ray intensity ratios for

platinum and lead agree well with

theoretical and others values. While the

measured values of K jump ratios and

jump factors are systematically lower than

the theoretical and others values. This

may be due to the uncertainty in the

estimation of t, which are systematically

higher than the theoretical values.

References

[1] Bennal A. S. and Badiger N. M., 2007. J.Phys. B: At. Mol. Opt. Phys. 40, 2189-2199.

[2] Veigele W. M. J. 1973. At. Data Tables5,51.

[3] Mallikarjuna M. L., Appaji Gowda S.B., Gowda R. and Umesh T. K. 2002.Radiat. Phys. Chem.65,217.

[4] Ayala A. P. and Mainardi R. T. 1996.Radiat. Phys. Chem. 47,177.

[5] Polat R., Orchan I. and Budak G.2004. Anal. Chem. Acta 505,307.

[6] Budak G. and Polat R. 2004. J.Quant. Spectrosc. Radiat. Transfer88,525.

[7] Ertugrul M., Karabulut A. and BudakG. 2002. Radiat. Phys. Chem. 64,1.

[8] Budak G., Karabulut A. and Erturul M.,

2003. Radiat. Meas. 37, 103-107.[9] Polat R., Budak G., Gurul A.,

Karabulut A and Ertugrul M. 2005.Radiat. Meas. 39,409.

[10] Nayak S. V. and Badiger N. M. 2006. J. Phys.

B: At. Mol. Opt. Phys. 39, 2893-2900.[11] Gudennavar S. B., Badiger N. M.,

Thontadarya S. R. and Hanumaih B. 2003.Radiat. Phys. Chem. 68, 721.

[12] Tertian R. and Claisse F. 1982. CamelotPress, Southampton, UK, p.20.

[13] Gerward L., Guilbert N., Bjorn Jensen K. andLevring H., 2001. Radiat. Phys. Chem. 60, 23.

[14] Hubbell J. H., 1989. NISTIR. 89.[15] Scofield J. H., 1973. Laboratory Report

UCRL-51326.[16] Berger M. J., Hubbell J. H. and Seltzer S. M.,

Chang J., Coursey J. S., Sukumar R. andZucker D. S., 2005. XCOM: Photon Cross

Section Database (version 1.3). NationalInstitute of Standards and Technology,

Gaithersburg, MD.

[17] Kaya N., Apaydin G. and Tirasolu E., 2011.Radiat. Phys. Chem. 80, 677.

[18] Cengiz E., Traolu E., Apaydn G., Aylikci

V., Kp Aylikci N. and Aksoy C., 2011.Radiat. Phys. Chem. 80(3), 328.

4


5/5

[19] Ertural B., Apaydin G., Cevik U., ErturulM. and Kobya A. I., 2007. Radiat. Phys.

Chem. 76, 15.[20] Durak R. and Ozdemir Y., 1998. J. Phys. B.,

31, 3575.

5

k-shell jump ratios and jump factors for platinum and lead

Documents