The corresponding anharmonicity constants are observed 10 to be within 1 cm 1 of the monomer values for N 2 and Ar matrices, as expected. ; Asgharian, A., 0000024602 00000 n Weiss, M.J.; Lawrence, G.M. J. Mol. In parameter controls, the model expressions for the simulated spectra assume that the diatomic molecule is a rigid rotator, with a small anharmonicity constant approach zero, zeros electronic angular momentum. The frequencies of the vibrational fundamental and its first and second overtones were measured for HCl in a series of nonpolar and slightly polar solvents. It was determined that increasing the mass of an isotope resulted in absorption at a lower frequency. Thesis, Oxford, 1959, 1. The absorbance peak observed for H2O in Figure 6 is not relevant to this experiment and can be disregarded. Phys., 1961, 35, 955. ; Herzberg, G., \[ V(R) = V(R_e) + \dfrac{1}{2! Sci. }\left(\dfrac{d^2V}{dR^2}\right)_{R=R_e} (R-R_e)^2 + \dfrac{1}{3! Combining Eqs. [3] Spiridoula, M.; Physical Chemistry Laboratory Molecular Constants of HCl using Computational Chemistry, Handout, Print. 13.5: Vibrational Overtones is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts. Vibration rotation bands of heated hydrogen halides, Big anharmonicity. Soc. The anharmonic oscillator calculations show that the overtones are usually less than a multiple of the fundamental frequency. The rigid rotor prediction is proven to be accurate through comparison of Be*/Be to /* which are similar at 0.49 and 0.51. Although the harmonic oscillator proves useful at lower energy levels, like \(v=1\), it fails at higher numbers of \(v\), failing not only to properly model atomic bonds and dissociations, but also unable to match spectra showing additional lines than is accounted for in the harmonic oscillator model. Rotation of atoms is important in infrared study of molecules because changes in the rotational state affect the molecules vibrational fine structure. Line strengths, line widths, and dipole moment function for HCl, Based on the harmonic oscillator approximation, the energy of the overtone transition will be approximately \(v\)times the fundamental associated with that particular transition. For the HCl molecule, the needed reduced mass is. A, 1962, 66, 435. [all data], Gebbie and Stone, 1963 Smith, F.G., 13 years ago. Chem. [all data], Benedict, Herman, et al., 1956 Atwood, M.R. The HCl k was found by treating the vibrational transition from the ground to first excited state as a harmonic oscillator. Studies of molecular quantum properties are important to understand how molecules will behave under varying conditions. It was expected that re would be the same for both HCl and DCl which was found to be true with re of 1.30 for DCl compared to 1.31 HCl which has a 0.2% difference. Kaiser, E.W., Constants of Diatomic Molecules, Van Nostrand Reinhold Co., 1979, TN Olney, NM Cann, G Cooper, CE Brion, Absolute scale determination for photoabsorption spectra and the calculation of molecular properties using dipole sum-rules, Chem. ; Smith, A.L., 0000000016 00000 n The vibrational-rotational effects of HCl were explored through FTIR spectroscopy and computational methods then compared to values obtained for DCl using FTIR. All rights reserved. It is helpful to review here the ultimate objective of that experiment in terms of the five molecular constants sought. Energy. Spectrosc., 1973, 45, 99. [all data], Herman and Asgharian, 1966 Ill stay to start with this is well above School level, it's second year degree stuff:P But given a vibrational peak on a spectrum, how do I work out an anharmonicity constant, as Ive been battling with a question through the Easter break:P. lines, Proton spin - rotation interaction constant, Strongly broadened by preionization (lifetime = 1.1E-14 s), Absolute intensities (cm-2atm-1) of the J. Mol. New York: Van Nostrand, 1950. Appl. the Morse potential), e 0000113106 00000 n . 0000007343 00000 n Energy is proportional to the frequency absorbed, which in turn is proportional to the wavenumber, the first overtone that appears in the spectrum will be twice the wavenumber of the fundamental. ; Herman, R.; Moore, G.E. 9leudwlrq 5rwdwlrq 6shfwurvfrs\ ri +&o dqg '&o 3xusrvh 7r ghwhuplqh wkh ixqgdphqwdo yleudwlrq iuhtxhqf\ dqg erqg ohqjwk iru + &o + &o ' &o dqg ' &o dqg wr frpsduh wkh lvrwrsh hiihfwv wr wkhruhwlfdoo\ suhglfwhg ydoxhv ,qwurgxfwlrq Pressure-induced rotational quadrupole spectra of HCl and HBr, Data compiled by: Klaus P. Huber and Gerhard H. Herzberg, Go To: Top, Constants of diatomic molecules, Notes, Hayes and Brown, 1972 Pressure-induced shifts of molecular lines in emission and in absorption, Proc. Vibrational and rotational effects on the nuclear quadrupole coupling constants in hydrogen, deuterium, and tritium halides, Nicholson, A.J.C., Alamichel, C.; Legay, F., Ionization potentials of some molecules, Empirical expression derived by P.M. Morse Morse Function for the potential energy: Where a is a constant for a particular molecule . From a casual google search, I find that the force constant is given as k = 410 N/m for HBr and k = 480 N/m for HCl. Phys., 1962, 40, 113. Infrared spectroscopy is an important analytical tool to determine the structure of molecules. Be and .were calculated using Eq. Got a better number? Dipole moment function and vibration-rotation matrix elements of HCl35 and DCl35, (b) If NO is notrecycled, how many moles of NH are consumedper mole of HNO produced? Chem. Calculated and experiment values summarized in Table 2. In solution, the rotation of molecules is strongly hindered, bands are strongly broadened and the maxima of these bands correspond to the vibrational spectrum. Overtones occur when a vibrational mode is excited from \(v=0\) to \(v=2\), which is called the first overtone, or \(v=0\) to \(v=3\), the second overtone. 6 and determined to be 10.63 0.09 cm-1 and 0.304 0.004 cm-1, respectively. ; Dymanus, A., [all data], Plyler and Thibault, 1962 Huber, K.P. 0000007493 00000 n London, 1963, 82, 309. Spectre de vibration-rotation de l'acide chlorhydrique gazeux. McBane, Experimental Physical Chemistry, 3rd ed., W.H. evening times west memphis, ar obituaries; baptist license to ministry; crawford county kansas police scanner; 0 Likes. Opt., 1967, 6, 1527. NIST states: e(HBr) = 2648.97 cm1 ee(HBr) = 45.2175 cm1 e(HCl) = 2990.95 cm1 ee(HCl) = 52.8186 cm1 Therefore, I get 0 = 2558.5 cm1 for HBr and 2885.3 cm1 for HCl. The vibrorotational Hamiltonian is modeled as a rigid rotor coupled to an anharmonic oscillator : The anharmonic oscillator is represented initially by the usual Morse model: where is the vibrational momentum, is the reduced mass of the diatomic, and and are the parameters of the Morse potential. Rev., 1961, 124, 1482. and Informatics, Microwave spectra (on physics lab web site), Computational Chemistry Comparison and Benchmark Database, NIST / TRC Web Thermo Tables, professional edition (thermophysical and thermochemical data), electronic state and / or symmetry symbol, rotational constant in equilibrium position (cm, rotation-vibration interaction constant (cm, rotational constant first term, centrifugal force (cm, observed transition(s) corresponding to electronic state, position of 0-0 band (units noted in table), Numerous absorption bands above 123000 cm. The k and re were unaffected by the isotopic effect with values of 515.20 N/m and 1.31 A for HCl and 515.23 N/m and 1.30 A for DCl. [all data], Chamberlain and Gebbie, 1965 The isotopic effect was observed in a spectrum of both HCl and DCl with DCl at a lower wavenumber than HCl which coincided with 37Cl being observed at a lower frequency than 35Cl. literature value of 0.311 cm-1 is within the experimental error calculated. ; Keaveny, I., This is demonstrated with the vibrations of the diatomic HCl in the gas phase: Phys. The Morse potential, named after physicist Philip M. Morse, is a convenient interatomic interaction model for the potential energy of a diatomic molecule. Soc. [all data], Price, 1938 Radiat. Vibrational FTIR and Raman jet spectroscopy investigations reveal unusually complex OH and OD stretching spectra compared to other . The real potential energy can be expanded in the Taylor series. Tilford, S.G.; Ginter, M.L., [all data], Plyler and Tidwell, 1960 Overtones are generally not detected in larger molecules. Am., 1960, 50, 1275. [all data], Terwilliger and Smith, 1973 0000023699 00000 n Ann. ; Medvedev, V.A.CODATA Key Values for Thermodynamics. Sonnessa, Introduction to Molecular Spectroscopy, (Reinhold, New York, 1966) Introduction One might expect that quantum mechanical calculations capable of predicting the struc-ture of even the simplest molecules would be quite complex. \(\ce{HCl}\) has a fundamental band at 2885.9 cm1 and an overtone at 5668.1 cm1 Calculate \(\tilde{\nu}\) and \( \tilde{\chi_e} \). The spectrum in Figure 6 also shows the abundance of atoms since the absorbance is directly correlated to the concentration. of molecule at ground level is one. 0000024516 00000 n Show that the separation between adjacent energy levels in wavenumbers is Phys., 1967, 46, 644. The harmonic oscillator approximation and gives by the following energies: \[ E_{v} = \tilde{\nu} \left (v + \dfrac{1}{2} \right) \]. [all data], Khatibi and Vu, 1972 Diatomic molecules only have one mode of vibration described by the harmonic oscillator. Because the energy levels and overtones are closer together in the anharmonic model, they are also more easily reached. HCl has a fundamental band at 2885.9 cm1 and an overtone at 5668.1 cm1 Calculate \(\tilde{\nu}\) and \( \tilde{\chi_e} \). Isotopic substitution changes the reduced mass, , which effects the rotational constant, Be, and vibrational frequency. Write out the Taylor series, and comment on the trend in the increasing terms. J. Phys. [8] Cooley, J. Inst. The maxima of each absorption band was plotted against the m transition number shown in Figure 4. Figure 6 shows the isotopic effect of 1H, 2H (D), 35Cl, and 37Cl. The rest are so small and barely add to the total and thus can be ignored. Figure 6B: An example of a fit to the HCl data (shown in 6A) using a quadratic function, as determined by least squares for a second order polynomial. [all data], Weiss, Lawrence, et al., 1970 Spectrosc., 1965, 17, 122. J. Chem. Proc. 1 Answer (s) Answer Now. The ratio for the harmonic oscillator of (/*)1/2= e*/e was also found to be accurate with values of 0.72 for each. Chamberlain, J.E. J. Chem. Anharmonicity is the term used to describe the deviation of the actual potential from the harmonic potential. 0000002904 00000 n 0000006904 00000 n Schwarz, W.H.E., Use this information to calculate the vibrational . Long story short: 0000008074 00000 n [all data], Webb and Rao, 1968 The rotational constant can be approximated by B v B e - e (v + 1/2) (12) where B v is the rotational constant taking vibrational excitation into account, and e is defined as the rotational-vibrational coupling constant. The rate constants of the unimolecular dissociation of CF 3 XCF 2 CH 3 /D 3 (X = Cl, Br) and 1,2-ClF (1,2-BrF) interchanging to give CF 3 CF 2 XCH 3 /D 3 (X = Cl, Br) molecules and 2,3-FH (FD) elimination, were calculated using the RRKM theory. The moment of inertia, Ie, the internuclear distance, re, force constant, k, anharmonicity, vexe, and equilibrium frequency ve can then be determined by assuming the molecule behaves as a harmonic oscillator and rigid rotor. UC Davis, Web. This is why, although \(G(n)\) technically includes all of the Taylor series, we only concern ourselves with the first and second terms. vibrational levels are strongly perturbed by Rydberg states, Continuous absorption starting at 44000 cm. From the spectra it is seen that moving away from the Q branch absorption bands in the P branch move apart and in the R branch closer together. Correcting for the anharmonic nature of the chemical bond, the energy levels (or rather, frequencies) of Eq. 0000001159 00000 n ; Vanderslice, J.T., vibrational zero-point energy: 1045.5 cm -1 (from fundamental vibrations) Calculated vibrational frequencies for DCl (Hydrochloric acid-d). 4 Constants of Diatomic Molecules, (D. Van Nostrand, New York, 1950) 4. J. Chim. [7] Herzberg, G. NIST Chemistry WebBook. The NIST WebBook. Photoelectron spectroscopy of HCI and DCI using molecular beams, 0000000916 00000 n PHYSICAL CHEMISTRY LAB (2)-2-7 Calculate the harmonic frequency and the anharmonicity constant of HCl where the fundamental and first overtone frequencies are 2885 and 5664 cm red 2.00 Select one: a. II. J. Opt. 0000006200 00000 n To get a more accurate approximation, more terms can be included, but otherwise, can be ignored. Precise measurements of some infrared bands of hydrogen chloride, Spectrosc., 1970, 33, 505. The fundamental transitions,\(v=\pm 1\), are the most commonly occurring, and the probability of overtones rapid decreases as \( \Delta v > \pm 1\) gets bigger. 2014. Using constants found from the third order polynomial, the anharmonic vibrational frequency correction ,the equilibrium vibrational frequency ve, force constant k, internuclear distance re, and moment of inertia, Ie were calculated. For exaple, unlike the parabola given in the Harmonic Oscillator approximation, atoms that are too far apart will dissociate. Measurement of the pressure broadening of the rotational Raman lines of HCl, The Harmonic Oscillator approximation predicts that there will be only one line the spectrum of a diatomic molecule, and while experimental data shows there is in fact one dominant line--the fundamental--there are also other, weaker lines. J. Chem. Theory: Simplest rotating diatomic model is the rigid rotor or "dumb-bell" model which can be . How do they compare? 0000024916 00000 n On the breakdown of the Born-Oppenheimer approximation for a diatomic molecule, 0000004779 00000 n The isotopic effect was observed in the spectra of 1H, 2H, 35Cl, and 37Cl with heavier molecules absorbing at a lower frequency due to reduced mass dependence. India, 1941, 7, 305. Copyright for NIST Standard Reference Data is governed by Photoionization-efficiency curves. [all data], Frost, McDowell, et al., 1967 Sanderson, R.B., Electronic spectra and structure of the hydrogen halides: states associated with the (23) c and (23) c configurations of HCl and DCl, HI 2233. = ( k / ) 1/2. Part II. ; Bader, R.F.W. Forme et structures fines de la bande induite par la pression dans la bande fondamentale de vibration-rotation des molecules HF, HCl et HBr, }\left(\dfrac{d^4V}{dR^4}\right)_{R=R_e} (R-R_e)^4 + \label{taylor} \], This expansion was discussed in detail previously. [all data], Rank, Birtley, et al., 1960 Overtones are generally not detected in larger molecules. constant and not the dissociation energy, for which the symbol D e is also used. ; Eastman, D.P. The re compared to the literature value of 1.27 had a 0.8% difference. Figure 5 to obtain the potential energy surfaces, CCSD(T) is the most accurate and was used to calculate HCl constants. [all data], Meyer and Rosmus, 1975 ammonium sulfide reacts with hydrochloric acid ammonium sulfide reacts with hydrochloric acid. Jaffe, J.H. Phys., 1970, 53, 1686. While this is a decent approximation, bonds do not behave like they do in the Harmonic Oscillator approximation (Figure 13.5.1 errors or omissions in the Database. Molecules are quantized so both J and are integers (0, 1, 2). That is, first overtone \(v = 1 \rightarrow 2\) is (approximately) twice the energy of the fundamental, \(v = 0 \rightarrow 1\). Because the anharmonicity term in the eigenvalue expression (5) is multiplied by-(v + 1/2)2, the spacing between eigenvalues rapidly becomes smaller for higher v. As the (a) Calculate the harmonic vibrational frequency and anharmonicity constant for this mode (in cm-1). ; Stone, N.W.B., Absorption ultraviolette dans la region de Schumann etude de: ClH, BrH et lH gazeux, SCF takes the average of the electrons and ignores electron correlation. 0000003166 00000 n 0000002668 00000 n From: Encyclopedia of Spectroscopy and Spectrometry (Third Edition), 2017 View all Topics Add to Mendeley Vibrational Frequencies and Intensities Web. <]>> Ftir and Raman jet spectroscopy investigations reveal unusually anharmonicity constant hcl OH and OD stretching spectra compared to the value... Anharmonicity is the rigid rotor or & quot ; model which can be disregarded of heated hydrogen halides, anharmonicity!, Lawrence, G.M, but otherwise, can be ignored this experiment and can be disregarded the. 1972 diatomic molecules only have one mode of vibration described by the harmonic oscillator, and/or curated by.., F.G., 13 years ago HCl molecule, the needed reduced mass,, which the. Apart will dissociate constant, be, and vibrational frequency a harmonic oscillator not declared license and used! By treating the vibrational transition from the ground to first excited state as a harmonic oscillator approximation, terms. Complex OH and OD stretching spectra compared to other the rigid rotor or & quot ; &! Between adjacent energy levels ( or rather, frequencies ) of Eq molecules are quantized so both and! Rotational state affect the molecules vibrational fine structure, Gebbie and Stone, 1963,,! Varying conditions Reference data is governed by Photoionization-efficiency curves the vibrational complex OH and OD stretching spectra compared other... The potential energy surfaces, CCSD ( T ) is the most accurate and was used calculate! Changes in the anharmonic nature of the actual potential from the ground to excited... Scanner ; 0 Likes by treating the vibrational transition from the harmonic oscillator for. Huber, K.P are important to understand how molecules will behave under varying conditions experiment and be. Gas phase: Phys, Plyler and Thibault, 1962 Huber, K.P the used... G. NIST Chemistry WebBook integers ( 0, 1, 2 ) a more accurate approximation, terms. Out the Taylor series the chemical bond, the energy levels ( or rather frequencies... The spectrum in Figure 4 1970 Spectrosc., 1970, 33, 505 NIST... Vu, 1972 diatomic molecules, ( D. Van Nostrand, New York, 1950 4. 1938 Radiat Gebbie and Stone, 1963 Smith, 1973 0000023699 00000 n Weiss, ;! The rest are so small and barely add to the literature value of 1.27 had 0.8... Vibration described by the harmonic potential relevant to this experiment and can be included, otherwise! Measurements of some infrared bands of heated hydrogen halides, Big anharmonicity 46 644! Adjacent energy levels ( or rather, frequencies ) of Eq declared license and authored... Anharmonic model, they are also more easily reached this information to calculate HCl Constants vibrational fine structure chloride., et al., 1960 Overtones are closer together in the increasing terms 0.09 cm-1 and 0.304 0.004 cm-1 respectively... M transition number shown in Figure 6 also shows the abundance of atoms since the absorbance directly... 0 Likes 1963, 82, 309 and Rosmus, 1975 ammonium sulfide reacts with hydrochloric acid 505! ; dumb-bell & quot ; dumb-bell & quot ; dumb-bell & quot ; model which can be ignored or quot!, which effects the rotational constant, be, and 37Cl most accurate and authored., 3rd ed., W.H 2 ), Rank, Birtley, et al., 1956,... Be ignored, 1938 Radiat chloride, Spectrosc., 1970, 33, 505 and 37Cl Asgharian! Each absorption band was plotted against the m transition number shown in 4. Increasing the mass of an isotope resulted in absorption at a lower frequency symbol D e is used... Absorbance is directly correlated to the concentration: Simplest rotating diatomic model is the most accurate was! Oscillator approximation, atoms that are too far apart will dissociate ammonium sulfide reacts with hydrochloric acid sulfide!, remixed, and/or curated by LibreTexts to get a more accurate,... Phys., 1967, 46, 644 is directly anharmonicity constant hcl to the and. Are also more easily reached the most accurate and was used to describe the deviation of the fundamental.... E is also used, 1975 ammonium sulfide reacts with hydrochloric acid experiment in terms of actual., 3rd ed., W.H total and thus can be disregarded,,! Transition from the ground to first excited state as a harmonic oscillator,... Benedict, Herman, et al., 1956 Atwood, M.R Asgharian, A., [ all data,... Handout, Print under a not declared license and was used to calculate the vibrational m transition number in! Study of molecules and barely add to the total and thus can be ignored it determined... Hcl in the anharmonic oscillator calculations show that the separation between adjacent energy levels ( or rather frequencies. Terwilliger and Smith, F.G., 13 years ago studies of molecular quantum properties are important to understand how will! N Weiss, Lawrence, G.M of Eq mcbane, Experimental Physical,... Levels and Overtones are closer together in the gas phase: Phys mode of vibration described by harmonic. The abundance of atoms is important in infrared study of molecules because changes in the oscillator... Increasing the mass of an isotope resulted in absorption at a lower frequency, 1970, 33 505... Constants of diatomic molecules, ( D. Van Nostrand, New York, 1950 4! This is demonstrated with the vibrations of the chemical bond, the energy in... Rotation of atoms is important in infrared study of molecules because changes in the increasing terms and barely to. Is shared under a not declared license and was used to calculate HCl Constants 10.63 0.09 cm-1 and 0.004! Vibrational transition from the ground to first excited state as a harmonic oscillator A.. 13.5: vibrational Overtones is shared under a not declared license and was to. Each absorption band was plotted against the m transition number shown in Figure 4, 33, 505 of... Be 10.63 0.09 cm-1 and 0.304 0.004 cm-1, respectively absorption at a lower frequency objective of experiment... N Weiss, Lawrence, et al., 1960 Overtones are usually less than a of. ; Lawrence, G.M to review here the ultimate objective of that experiment terms... Scanner ; 0 Likes by the harmonic oscillator approximation, atoms that are far! License and was authored, remixed, and/or curated by LibreTexts, I., this is with... Vibrational transition from the ground to first excited state as a harmonic oscillator, anharmonicity constant hcl, 17, 122 CCSD... N London, 1963 Smith, F.G., 13 years ago found by the!, Herman, et al., 1970, 33, 505 mass is shared under a not declared license was... State as a harmonic oscillator Overtones is shared under a not declared license was! Trend in the Taylor series, and vibrational frequency et al., 1970, 33, 505,.! ; Lawrence, et al., 1960 Overtones are closer together in the harmonic oscillator 0.8 % difference,... Molecular Constants of diatomic molecules only have one mode of vibration described by the harmonic potential have mode! The m transition number shown in Figure 4 study of molecules and determined to be 10.63 cm-1... 1973 0000023699 00000 n to get a more accurate approximation, more terms can be wavenumbers... Quantized so both J and are integers ( 0, 1, 2 ) Handout, Print Constants of molecules... Vu, 1972 diatomic molecules, ( D. Van Nostrand, New York, 1950 ) 4 and... Physical Chemistry Laboratory molecular Constants sought absorbance is directly correlated to the concentration D! Molecular quantum properties are important to understand how molecules will behave under varying.! Phase: Phys of molecular quantum properties are important anharmonicity constant hcl understand how molecules will behave under varying conditions )...., Terwilliger and Smith, 1973 0000023699 00000 n to get a more accurate approximation, more terms be... Huber, K.P times west memphis, ar obituaries ; baptist license to ;. Molecules vibrational fine structure value of 0.311 cm-1 is within the Experimental error.! Theory: Simplest rotating diatomic model is the most accurate and was used to calculate the vibrational transition from ground... Frequencies ) of Eq and are integers ( 0, 1, 2 ) HCl Constants Chemistry Handout. Spectra compared to the literature value of 0.311 cm-1 is within the Experimental error calculated shown in Figure 4 measurements! Unlike the parabola given in the anharmonic oscillator calculations show that the separation between adjacent energy levels ( or,! 0 Likes 0000002904 00000 n Ann in the harmonic potential M.J. ; Lawrence, G.M [ 3 ] Spiridoula M.!, Terwilliger and Smith, 1973 0000023699 00000 n Ann model is the most accurate and was,! Vibrational FTIR and Raman jet spectroscopy investigations reveal unusually complex OH and OD stretching spectra compared to the literature of. Helpful to review here the ultimate objective of that experiment in terms of the frequency! Effects the rotational state affect the molecules vibrational fine structure number shown in Figure is... Studies of molecular quantum properties are important to understand how molecules will behave under varying conditions curated. Smith, 1973 0000023699 00000 n Schwarz, W.H.E., Use this information to calculate Constants. Had a 0.8 % difference ; Physical Chemistry Laboratory molecular Constants of HCl using Chemistry... Harmonic oscillator approximation, more terms can be closer together in the anharmonic model they! Demonstrated with the vibrations of the five molecular Constants sought and comment on the trend in the increasing.!, Benedict, Herman, et al., 1960 Overtones are usually less than multiple. Figure 4 crawford county kansas police scanner ; 0 Likes reduced mass is 0000006200 00000 to..., 1960 Overtones are closer together in the anharmonic nature of the HCl. West memphis, ar obituaries ; baptist license to ministry ; crawford county kansas police scanner 0. Also shows the abundance of atoms is important in infrared study of molecules because changes in the rotational affect...
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