Total Collision Cross Sections for the Interaction of Atomic Beams of Alkali Metals with Gases
dc.contributor.author | Rothe, Erhard W. | en_US |
dc.contributor.author | Bernstein, Richard B. | en_US |
dc.date.accessioned | 2010-05-06T22:12:04Z | |
dc.date.available | 2010-05-06T22:12:04Z | |
dc.date.issued | 1959-12 | en_US |
dc.identifier.citation | Rothe, Erhard W.; Bernstein, Richard B. (1959). "Total Collision Cross Sections for the Interaction of Atomic Beams of Alkali Metals with Gases." The Journal of Chemical Physics 31(6): 1619-1627. <http://hdl.handle.net/2027.42/70463> | en_US |
dc.identifier.uri | https://hdl.handle.net/2027.42/70463 | |
dc.description.abstract | Total collision cross sections (Q) for the interaction of atomic beams of K and Cs with a number of molecules were measured with an apparatus of 30″ angular resolution. Although absolute determinations of Q are difficult, relative values are readily obtained (±3%). Results are reported as the ratio (Q*) of the cross section for a given molecule to that of argon for the same beam atom. Seventy‐seven molecules (of varied complexity and reactivity) were studied with K and 16 with Cs beams. Q* ranged from 0.29 to 2.8.The data were correlated using the Massey‐Mohr theory, assuming an attractive intermolecular potential V(r) = —C/r6. For this case Q=b(C/vr)2/5, where vr is the relative velocity and b a known constant. C was estimated from standard formulas for the London dispersion and dipole‐induced dipole forces, using known refraction and dipole moment data. The theoretical values of Q differ by a nearly constant factor from the experimental results; thus values of Q* are predicted with good accuracy. The deviation between Qcalc* and Qobs* was <±3% for 57% (and <±10% for 87%) of the molecules. Most of the large deviations occurred for the light gases. | en_US |
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dc.format.extent | 546961 bytes | |
dc.format.mimetype | text/plain | |
dc.format.mimetype | application/pdf | |
dc.publisher | The American Institute of Physics | en_US |
dc.rights | © The American Institute of Physics | en_US |
dc.title | Total Collision Cross Sections for the Interaction of Atomic Beams of Alkali Metals with Gases | en_US |
dc.type | Article | en_US |
dc.subject.hlbsecondlevel | Physics | en_US |
dc.subject.hlbtoplevel | Science | en_US |
dc.description.peerreviewed | Peer Reviewed | en_US |
dc.contributor.affiliationum | Chemistry Department, University of Michigan, Ann Arbor, Michigan | en_US |
dc.description.bitstreamurl | http://deepblue.lib.umich.edu/bitstream/2027.42/70463/2/JCPSA6-31-6-1619-1.pdf | |
dc.identifier.doi | 10.1063/1.1730662 | en_US |
dc.identifier.source | The Journal of Chemical Physics | en_US |
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dc.identifier.citedreference | As pointed out by Rosin and Rabi,2 this equation is an approximation to the accurate one which involves a tedious numerical integration. Appendix I summarizes a number of calculations which show the validity of the approximation in the present case. | en_US |
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dc.identifier.citedreference | The changes in Q were probably due primarily to changes in resolution. The largest effects were noted when the slits were cleaned or reset. When the slits began to clog, Q increased (presumably on account of the narrower beam); after cleaning the slits, Q decreased. Improper beam alignment also led to decreased values of Q. | en_US |
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dc.identifier.citedreference | If T1T1 and T2T2 are the temperatures (°K) of the different species, the appropriate substitution † would be T = 2T1T2/(T1+T2).T=2T1T2∕(T1+T2). It is to be noted that Eq. (5) is valid only for rrmin = (μ1μ2/kT)⅓;rrmin=(μ1μ2∕kT)13; thus for μ1 = μ2 = 1Dμ1=μ2=1D and T = 300 °K,T=300°K, rmin = 2.9A;rmin=2.9A; for μ1 = 1Dμ1=1D and μ2 = 10D,μ2=10D, rmin = 6.2 A.rmin=6.2A. | en_US |
dc.identifier.citedreference | The polarizabilities of K and Cs were taken to be 34.0 and 42.0 A3A3, respectively [H. Scheffers and J. Stark, Physik. Z. 35, 625 (1934) ]. The units of μ1μ1 and α1α1 are debyes and A3,A3, respectively. N is obtained by summing the periodic table group numbers for each constituent atom in the scattering molecule (N = 8N=8 for the noble gases, except for He, where N = 2N=2). | en_US |
dc.identifier.citedreference | The same conclusion results from substituting for the denominator a term proportional to 1/I1+1/I21∕I1+1∕I2 (where the I’s are the first ionization potentials of the two species). | en_US |
dc.identifier.citedreference | R. A. Buckingham (private communication), March 17, 1959. | en_US |
dc.identifier.citedreference | See, for example, L. Loeb, Kinetic Theory of Gases (McGraw‐Hill Book Company, Inc., New York, 1934), p. 95. | en_US |
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dc.identifier.citedreference | Any impurity in the neon would lead to a greater apparent cross section, since Ne is the least effective molecule for beam scattering of those studied. Molecules with lower cross section are known, but these have smaller mass (and thus higher speeds), making them more efficient scatterers. | en_US |
dc.owningcollname | Physics, Department of |
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