Theory of Scattering according to Majorna

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    6

    THE THEORY OF SCATTERING

    6.1. SCATTERING FROM A POTENTIALWELL

    The author studied here the problem of the scattering of a plane wavefrom a one-dimensional square potential well. All the physically inter-esting cases were treated.

    e= h/2=m = 1.

    2 + 2(E V)= 0.V = 0:

    y + 2Ey= 0.

    2E=k2,

    y1= eikx, y2 = e

    ikx.

    y + 2(E U)y= 0,U= V,

    y + 2(E+ V)y= 0.

    2(E+ V) =2, 2E=k2,

    = k

    1 +

    V

    E.

    By imposing the matching conditions for the wavefunction and its deriva-tive, one obtains:

    311

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    312 E. MAJORANA: RESEARCH NOTES ON THEORETICAL PHYSICS

    y=

    1 + 1 + VE

    2 e

    ik(x+a)ia

    +

    1 1 + VE

    2 e

    ik(x+a)ia

    ,x < a,

    eix,

    g= 1 +

    1

    2

    V

    E

    a < x < a,

    1 +

    1 + VE

    2 eik(xa)+ia +

    1

    1 + VE

    2 eik(x+a)+ia,

    a < x,

    E >0,

    E=1

    2 2 V, E=1

    2 k2,

    = k

    1 +

    V

    E, k=

    1 + VE

    .

    g gives the ratio of the wave amplitude inside and outside the well. 1

    E V: 1 +

    V

    E =i

    V

    E 1,

    = ik

    V

    E 1 =k1

    V

    E 1, k1=ik.

    1@That is: g is given by the ratio a2+ b2/c2 wherea [b] is the coefficient of the first [second]wave term in the first or third row, whilec is the coefficient of the wave term in the secondrow (c = 1). Note that the quantity we call g, here and in what follows, is in the originalmanuscript denoted byy, the same as the symbol there used for the wave function.

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    THE THEORY OF SCATTERING 313

    y=

    1 + i VE 1

    2 e

    k1(x+a)ia

    +

    1 i VE 1

    2 e

    k1(x+a)ia

    ,x < a,

    eix, a < x < a,

    1 + i

    VE 1

    2 ek1(xa)+ia +

    1 i

    VE 1

    2 ek1(xa)+ia,

    a < x,

    V < E

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    314 E. MAJORANA: RESEARCH NOTES ON THEORETICAL PHYSICS

    y=

    1 +

    V

    E cos a sin k(x + a) sin a cos k(x + a),

    x 0:1st approximation:

    = 2ih

    k0e2i(h/2m)(220)t,

    = 2mh2(2 20 )k0

    e2i(h/2m)(2

    2

    0)t 1 + ( 0) .4@Here the author denotes with0 =p0/hthe momentum (divided byh) of the free particle,while(x) signifies the Dirac delta-function.

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    318 E. MAJORANA: RESEARCH NOTES ON THEORETICAL PHYSICS

    2nd approximation:

    =

    2i

    h

    k0e2i(h/2m)(220)t +

    4im

    h3 kk0

    1

    2

    2

    0

    e2i(h/2m)(22

    0)t e2i(h/2m)(22)t

    d,

    = 2mh2(2 20 )

    k02 20

    e2i(h/2m)(

    220)t 1

    +4m2

    h4

    kk0

    e2i(h/2m)(

    220)t 1

    (2 20 )(2 20 )

    e2i(h/2m)(22)t

    1(2 2)(2 20 )

    d + ( 0) .

    In first approximation, for =0, we have:

    ||2 = 16m2

    h4(2 20 )2|k0 |2 sin2

    h(2 20 )t2m

    .

    Neglecting constant terms, for t we get:

    ||2 =82mh3

    |k0|2 t

    2 20

    ,

    and the transition probability is:

    P0=82m

    h3 |k0|2

    2 20

    .

    In second approximation:

    ||2 = 16m2h4(2 20 )2

    |k0 |2 sin2h(2 20 )t2m

    + 32m3

    h6(2 20 ) sin

    h(2 20 )t2m

    k0kk0+ k0kk0

    sin h(2 2)t/2m(2 2)(2 20 )

    sin h(2 20 )t/2m

    (2 20 )(2 20 )

    d.

    6.3.1 Coulomb Field

    For a Coulomb field:

    V =C

    r =

    Ve

    2i(xx+yy+zz) dx dy dz,

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    THE THEORY OF SCATTERING 319

    V=C

    e2iq

    r dq= C

    0

    2

    sin2r dr=

    C

    2;

    k

    =V

    =

    C

    | |2 .In first approximation:

    P0= 8mC2

    h3| 0|4

    2 20

    = mC2

    2h340sin4 /2

    2 20

    .

    In second approximation, for =0: 5

    =

    2m

    h2

    1

    2 20C

    ( 0)2 e2i(h/2m)(220)t

    1

    +4m2

    h4

    C2

    2| |2| 0|2

    e2i(h/2m)(22

    0)t 1(2 20 )(2 20 )

    e2i(h/2m)(22)t 1(2 2)(2 20 )

    d.

    6.4. THE BORN METHOD

    The scattering from a given center was studied here by means of the Bornmethod, and approximated expressions for the scattered partial waveswere obtained.

    2 + k2 = F .

    =0+ 1+ 2+ . . . ,

    2 0+ k

    20 = 0,

    2 1+ k

    21 =F 0,

    2 2+ k

    22 =F 2,

    . . . ,

    2 n+ k

    2n=F n1,

    . . . .

    5@Probably, the author started to evaluate the transition probability for Coulomb scatteringin a second approximation, but succeeded only in obtaining an expression for the coefficient.

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    320 E. MAJORANA: RESEARCH NOTES ON THEORETICAL PHYSICS

    n(q) = 14

    eik|qq

    |

    |q q| F(q) n1(q

    ) dq.

    0(q) = eiku0q,

    1(q) = 14

    eik|qq

    |

    |q q| eiku0q F(q) dq,

    2(q) = 1

    162

    eik|qq

    |

    |q q|eik|q

    q|

    |q q| eiku0q F(q) F(q) dq dq,

    |u0| = 1.|q| =r :

    1(q) = 14r

    eik|qq

    | eiku0q

    F(q) dq.

    |q| =r, q=r u, |u| = 1;|q| =r , q =r u, |u| = 1,

    r :|q q

    | =r r

    u u

    ,

    1(q) = eikr

    4r

    eikr

    (u0u)u F(q) dq.

    2(q) = eikr

    162r

    eik|q

    q|

    |q q| eikru0u eikr

    uu F(q) F(q) dq dq.

    q =q +:

    2(q) = eikr

    162r

    eik(u0u)q

    F(q) dq

    eik||

    || eiku0 F(q +) d.

    F = 1

    2

    Fe

    iq d,

    F=

    Feiq dq,

    eiq

    eikr

    r dq=

    4

    2 k2 ,

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    THE THEORY OF SCATTERING 321

    r :1(q) = e

    ikr

    4 Fk(uu0),

    2(q) = eikr

    162r

    eik(u0u)q

    F(q) dq

    2

    |ku0+ |2 k2Feiq d

    = eikr

    162r

    2

    |ku0+ |2 k2 Fd

    ei(ku0ku+)q

    F(q) dq,

    2(q) = eikr

    82r FFk(uu0)

    |ku0+

    |2

    k2

    d

    2(q) = eikr

    82r

    Fku0Fku

    2 k2 d.

    6.5. COULOMB SCATTERING

    The Schrodinger equation for the scattering of a wave from a Coulombpotential is solved and, in particular, the phase advancement is evaluated.

    Ze charge of the scatterer;

    Ze charge of the incident particle;

    Mmass of the incident particle.

    We adopt units such that M= 1, ZZe2 = 1, h/2= 1. It follows that:

    the length unit ish2/42M ZZe2 = (m/M) (1/ZZ) a0; 6

    the energy unit is 42M Z2Z2e4/h2 = 2(M/m) Z2Z2 Rh; 7

    the velocity unit is 2Z Ze2/h = ZZ/137c, where 1/137 =e2/(1/2)hc.

    The Schrodinger equation is:

    2

    + 2

    E1

    r

    = 0.

    6Here m denotes the electron mass and a0 0.529109 the Bohr radius.

    71 Rh = 13.54 V [Remember that the symbolV used by Majorana should more appropriatelyunderstood as eV].

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    322 E. MAJORANA: RESEARCH NOTES ON THEORETICAL PHYSICS

    =n

    =0

    X(r)

    r P(cos ),

    X +

    k2 2r ( + 1)

    r2

    X= 0,

    k2 = 2E (the velocity of the ingoing particle in large units is v =(ZZ/137)c k).

    X = X1 + X2,

    X1

    = x+1

    eikx

    F

    + 1 +

    i

    k , 2 + 2,2ikx ,X2 = x+1 eikx F

    + 1 i

    k, 2 + 2, 2ikx

    ,

    F( ,,x) = 1 +

    x +

    ( + 1)

    2!(+ 1)x2 +

    ( + 1)( + 2)

    3!(+ 1)(+ 2)x3 + . . . .

    Alternative solution

    X +

    k2 2r ( + 1)

    r2

    X = 0,

    takes non-integer values greater than1/2,

    X =r+1 u,

    u + 2 + 1r

    u +

    k2 2r

    u= 0.

    [8]

    u +

    0+

    1r

    u +

    0+

    1r

    u= 0,

    0= 0, 1 = 2( + 1), 0 =k2, 1= 2:

    u eiktr (t 1)+i/k (t + 1)i/k dt.8@ This equation is a particular case of the more general one reported just after it, and isalso considered by the author in another place; see Appendix6.10.

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    THE THEORY OF SCATTERING 323

    [...]9

    |Im log(1 t)| ,|Im log(1 + t)| :

    u=

    1

    1eiktr (1 t)+i/k (1 + t)i/k dt .

    For r= 0, on setting 1 t= 2x:

    u(0) =

    11

    (1 t)+i/k (1 + t)i/k dt= 1

    0(2x)i/k (2 2x)+i/k 2dx

    = 22+1 1

    0

    (x)i/k (1

    x)+i/k dx,

    u(0) = 22+1 ( + 1 i/k) ( + 1 + i/k)

    (2 + 2) . (1)

    |r| >0:u= u1 + u2,

    u

    1

    = e

    i(/2)(+1+i/k)

    e

    ikx 0 e

    krp

    p

    +i/k

    (2 + ip)

    ik

    dp,

    u2 = ei(/2)(+1i/k) eikx

    0ekrp p+i/k (2 ip)+ik dp.

    For real r we have u2 =u1.

    u1 = (kr)(+1) ei(/2)(+1+i/k)(i/k)log kr eikr

    0 ep

    p+i/k

    (2 + ip/kr)ik

    dp.

    For r :u1 = (kr)(+1) e/2k ei(/2)(+1) eikr(i/k)log kr 2i/k ( + 1 + i/k)

    = 2(kr)(+1) e/2k ei(/2)(+1) eikr(i/k) log2kr ( + 1 + i/k).

    Now, replace with ; the phase advancement becomes then:

    k= 2 arg ( + 1 + i/k)( + 1 + i/k) .

    9@ The author then evaluates u and u and verifies that the assumed form for u satisfiesthe previous differential equation.

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    324 E. MAJORANA: RESEARCH NOTES ON THEORETICAL PHYSICS

    1/4> a >0:

    ( ) ( + 1 ) = ( + 1) a, +1

    2 2 = +1

    2

    2 a,

    = +1

    2

    +

    1

    2

    2 a.

    6.6. QUASI COULOMBIAN SCATTERINGOF PARTICLES

    Let us assume a scattering potential of the form:

    kr2 + a2

    , (1)

    a being the magnitude of the radius of the scatterer. By denoting withT the kinetic energy of the incident particles, let us define the minimumapproach distance10 b in the limit Coulomb field (a= 0) as:

    k

    b =T; b=

    k

    T. (2)

    The scattering intensity under an angle will be obtained on multi-plying that appearing in the Rutherford formula by a numerical factordepending on the mutual ratios ofa,b,/2 (being the wavelength of

    the free particle) and. Let us set:

    i= f( ,,) iR, (3)

    whereiR is the intensity calculated from the Rutherford formula (a= 0)and

    = a

    /2, =

    b

    /2. (4)

    Since for a= 0 the Rutherford formula is exact, we have:

    f(0, , ) = 1. (5)

    10@ That is, the scattering parameter.

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    THE THEORY OF SCATTERING 325

    Let us now consider a fixedand take the limit 0. At zeroth orderapproximation, i.e., exactly for = 0, we can use the Wentzel method.By choosing as mass unit M, wavelength unit /2 and velocity unit v

    for the incident particles, from = h/Mv it follows that h= 2 in ourunits. Moreover, the kinetic energy of the incident particle is 1/2.From Eqs. (4) and(2) it follows that b = , k = /2 and a = . Bysubstituting these into Eq. (1), we get the expression for the potentialenergy, and the Schrodinger equation corresponding to the eigenvalue1/2 will be:

    2 +

    1

    r2 + 2

    = 0. (6)

    Let us set:

    =0+ 1+ 2+ . . . ,

    where:

    2 n+ n =

    r2 + 2

    n1. (7)

    In order to avoid convergence problems, instead of /

    r2 + 2 let us

    consider the expression

    1/r2 + 2 1/R for r < R and 0 for r >R; in the final results we will take the limit R . Eq. (7) is thenreplaced by: 11

    2 n+ n =P n1; (8)

    P =

    1r2 + 2

    1R

    , for r < R;

    0, for r > R.

    Setting0= eiz, we have:

    2 1+ 1 =Pe

    iz. (9)

    For an univocal solution of Eq. (9) we will choose 1 to represent a

    diverging wave. In this case Eq. (9) can be integrated and, putting

    r12 =

    (x x)2 + (y y)2 + (z z)2,

    11@ In the original manuscript, the factor is lacking.

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    326 E. MAJORANA: RESEARCH NOTES ON THEORETICAL PHYSICS

    we get:

    1(x,y,z) = 1

    4

    P(x

    , y

    , z

    )

    ei(r12+z)

    r12 dx

    dy

    dz

    . (10)

    Assuming the point (x,y,z) to be far from the origin, we have (r is thedistance from the origin, the angle between the vector radius and thez-axis):

    r : 1(r, ) = 14r

    P(x, y, z) eir

    eir(cos cos cos sin sin cos ) dxdydz,

    cos (1 cos ) sin sin cos

    = 2 sin /2

    sin /2 cos cos /2 sin cos = 2 sin /2

    cos(/2 /2)cos + sin (/2 /2)sin cos ,

    r : 1(r, ) = eir

    2 r sin /2

    0rP(r) sin

    2 sin /2r

    dr,

    (11)whence we easily deduce:

    f(, 0, ) = 2

    sin /2

    0

    rP(r) sin

    2 sin /2 r

    dr. (12)

    In we simply replace P with /r2 + 2, the integral in Eq. (12) doesnot converge; however, we can circumvent this difficulty by keeping in-determinate the upper integration limit and assuming, for the resultingintegral, its mean value which for the upper limit tends to infinity. Wethus find:

    f(, 0, ) = 2 sin /2

    0

    rr2 + 2

    sin (2 sin /2r) dr

    =

    0

    x sin x dxx2 + 42 sin2 /2

    = ( sin /2) .(13)

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    THE THEORY OF SCATTERING 327

    6.6.1 Method Of The Particular Solutions

    u +

    1

    r2 + 2 ( + 1)

    r2

    u = 0. (14)

    For the hydrogen atom we consider the values = 0.4, 0.5, 0.6, 0.7and = 0, 0.2, 0.4, 0.6, 0.8, 1. The solution of Eq. (14) is reportednumerically in the following tables for= 0 and= 0.4. 12

    = 0 = 0.2 = 0.4

    r

    0

    0.1

    0.2

    0.3

    0.4

    0.5

    0.6

    0.7

    0.8

    0.9

    1.0

    1.1

    1.2

    1.3

    u u

    u

    0 1 0.400

    1.019

    0.1018 0.305

    1.049

    0.2067 0.207

    1.070

    0.3137 0.109

    1.080

    0.4217 0.000

    1.080

    0.5297 -0.106

    1.069

    0.6366 -0.212

    u u

    u

    0 1 0

    u u

    u

    0 1 0

    12@ The author uses a numerical algorithm (unknown to us) in order to infer the solutionu(r) of Eq. (14) from its second (and first) derivative, and the first few results obtained aredisplayed in the tables.

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    328 E. MAJORANA: RESEARCH NOTES ON THEORETICAL PHYSICS

    = 0.6 = 0.8 = 1.0

    r

    0

    0.1

    0.2

    0.3

    0.4

    0.5

    0.6

    0.7

    0.8

    0.9

    1.0

    1.1

    1.2

    1.3

    u u

    u

    0 1 0

    u u

    u

    0 1 0

    u u

    u

    0 1 0

    6.7. COULOMB SCATTERING: ANOTHERREGULARIZATION METHOD

    Let us assume the potential to be as follows:

    V =

    V0, for r < R,

    k/r, for r > R.(1)

    r

    V

    R

    V0

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    THE THEORY OF SCATTERING 329

    Denoting with T the kinetic energy of the incident particles, the mini-mum approach distance in the Coulomb field will be:

    b= k

    T. (2)

    The scattering intensity under an angle will be given by the productof the intensity scattering due to the Coulomb field, obtained from theRutherford formula, times a numeric function depending on,R/,b/,V0/T:

    13

    f

    V0T

    , R

    /2,

    b

    /2,

    , (3)

    where is the wavelength of the free particle. Let us choose as massunitM, velocity unitv and length unit/2relative to the free particle.In such units, h= M v 14 is equal to 2, while T is 1/2. Moreover, letus set:

    A=V0

    T , =

    R

    /2, =

    b

    /2, (4)

    so that:

    i

    iR =fV0

    T ,

    R

    /2 ,

    b

    /2 ,

    =f(A, ,,). (5)

    In our units we have:

    V0=A

    2, R= , b= , k=

    1

    2, (6)

    and the Schrodinger equation corresponding to the eigenvalue 1/2 takesthe form:

    2 + (1 A) = 0, for r < R,

    2 +

    1

    r

    = 0, for r > R.

    (7)

    For the hydrogen we have:

    = 0.4, 0.5, 0.6, 0.7;

    = 0.4, 0.5, 0.6, 0.7, 0.8;

    A= (2), (1.5), 1, 0.5, 0,

    0.5,

    1,

    1.5, 2,

    2.5,

    3,

    3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8.

    13@ In the original manuscript, the first dependent variable in Eq. (3) is V0/2T rather thanV0/T. However, in the following the author considered the latter parametrization.14@ In the original manuscript, the author wrote erroneouslyh= /Mv.

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    330 E. MAJORANA: RESEARCH NOTES ON THEORETICAL PHYSICS

    6.8. TWO-ELECTRON SCATTERING

    v, v be the velocities of the two beams;

    n0, n0 be the rest numberdensities of the two beams;

    n= n0/

    1 v2/c2, n =n0/

    1 v2/c2 be thenumberdensitiesin the laboratoryreference frame;

    vr be the relative velocity according to the relativistic kinematics;

    S(vr) be the cross section.

    The number Nof collisions for unit volume and time can be written as:

    N=a

    v, v

    n n =S(vr) n0 n0

    vr1 v2r /c2

    .

    In terms ofa we thus have:

    S= a

    vr

    1 v2r /c2

    1 v2/c2

    1 v2/c2(classically(that is: non relativistically), we have insteadS=a/|vv|).Without considering the resonance in the scattering cross section, let u

    (0 u vr) be the velocity of the first electron after the collision in itsinitial reference frame; we have:

    dS=S(vr, u) du.

    Let us now denote with u1 the relative velocity between the frame ofthe first electron before (after) the collision and that of the second elec-tron after (before) the collision. By taking into account the resonancebetween the two electrons, u andu1 are indistinguishable. Putting, con-

    ventionally, u u1, the maximum value ofu is given by 15

    :

    umax=umin=c

    1 4 (1 v2r /c2)1 +

    1 v2r /c2

    2 = y2

    2 y2

    c2

    y=c

    1

    1 v2r /c2

    1 +

    1 + v2r /c2

    .

    The relation between u andu1 is the following:

    11 u2/c2 +

    11 u21/c2

    = 1 + 11 v2r /c2

    .

    15In this case we have u= u1

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    THE THEORY OF SCATTERING 331

    6.9. COMPTON EFFECT

    n= n0/1 v2/c2, number of electrons per cm3;

    n0, rest numberdensities of the electron beams;

    N, number of photons 16 per cm3;

    N0 =N 0/, number of photons per cm3 in the electron frame;

    h, energy of one photon;

    h0, energy of one photon in the electron frame (before or after

    the collision);u1, relative velocity between the ingoing electron frame and theoutgoing one (according to relativistic kinematics);

    S(0), cross section.

    The number of collisions for unit volume and time is thus:

    S(0) n0 N0 c= a n N,

    so that, in terms ofa,

    S(0) =a

    c

    11 v2/c2

    0.

    The differential cross section can be written as:

    dS=F(0, u) du,so that

    S=

    0

    F(0, u) du.

    Classically, the cross section is given by:

    Sclass =8

    3

    e4

    m2c4.

    16@ For the sake of clarity, here and in the following we have translated with photonswhat was termed quanta in the original manuscript.

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    332 E. MAJORANA: RESEARCH NOTES ON THEORETICAL PHYSICS

    6.10. QUASI-STATIONARY STATES

    The author considered the transition from a discrete (unperturbed) state0 with energy E0 to a continuum (perturbed) state , assuming thatthe unperturbed system has two continuum spectra W and W withenergyE0+W. What here reported are the scratch calculations whichprepared the Sect. 28 of Volumetto IV, to which we refer the reader

    for notations and further explanations of the arguments treated by theauthor. However, a further generalization is present here with respect towhat considered after Eq. (4.499) of Volumetto IV.

    = 12/Q2 + 2Q2

    IQ2

    0+ 2|I|2Q4

    W |I|2Q2

    W

    W WdW

    +2IL

    Q4 W IL

    Q4

    W

    W WdW

    +I

    e2i(

    )t/hdW

    (2/Q2 + 2Q2)(W W) 0

    + |I

    |2

    Q2 e2i()t/hW

    (2/Q2 + 2Q2)(W W) dW

    |I|2

    e2i()t/hdW

    (2/Q2 + 2Q2)(W W)

    WdW

    W W

    +IL

    Q2

    e2i(

    )t/hW

    (2/Q2 + 2Q2)(W W) dW

    IL e2i(

    )t/hdW

    (2/Q2 + 2Q2)(W

    W)

    WdW

    W

    W

    +|L|2Q2

    W ILQ2

    W.

    =

    A 0+ B W+ CW+

    b WdW

    +

    c WdW

    e2iEt/h,

    QuantityA:

    1

    (2/Q2 + 2Q2)( ) = Q2

    ( + iQ2)( iQ2)( ) ,

    R1 = e2it/h e2

    2Q2t/h 1

    2i( + iQ2),

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    THE THEORY OF SCATTERING 333

    R2 = 1

    2/Q2 + 2Q2,

    2i R1+1

    2 R2

    =

    1

    2/Q2 + 2Q2

    e

    2it

    e

    22Q2t/h

    Q2

    + i

    i

    ,

    A= 1

    2/Q2 + 2Q2

    I

    Q2

    1 e2it/h et/2T

    Ii

    1 e(2i/h)t et/2T

    ,

    A= I + iQ2

    1 e2it/h et/2T

    .

    QuantityB:

    1

    2/Q2 + 2Q22|I|2

    Q4 +

    2|I|22/Q2 + 2Q2

    +|L|2

    Q2 =

    1

    Q2 |I|2 + |L|2

    = 1,

    B = 1.

    QuantityC:

    1

    2/Q2 + 2Q22IL

    Q4 +

    2IL

    2/Q2 + 2Q2 IL

    Q2 = 0,

    C= 0.

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    334 E. MAJORANA: RESEARCH NOTES ON THEORETICAL PHYSICS

    Quantityb: 17

    e2i(

    )t/hd

    (2/Q2 + 2Q2)(

    )(

    )

    =

    Q2e2i(

    )t/hd

    ( + iQ2)( iQ2)( )( ) ,

    2i

    R0+1

    2R1+

    1

    2R2

    ,

    R0= e2it/h e2

    2Q2t/h 1

    2i( + iQ2)( + ipiQ2) ,

    R1 = 12/Q2 + 2Q2

    1 ,

    R2= e2i(t/h 1

    2/Q2 + 2Q21

    .

    2i

    R0+1

    2R1+

    1

    2R2

    =

    1

    2/Q2 + 2Q21

    2/Q2 + 2Q2

    e2it/h et/2T Q2 i

    Q2 i

    2

    Q2+ 2Q2

    i

    +

    2

    Q2+ 2Q2

    ie2i (

    )t/h

    ,

    b = |I|2

    Q21

    1

    2/Q2 + 2Q2+

    |I|2Q2

    1

    e2i(

    )t/h

    2/Q2 + 2Q2

    + |I

    |2

    2/Q2 + 2Q21

    2/Q2 + 2Q2

    e2it/h et/2T

    Q2 i

    Q2 i

    2

    Q2+ 2Q2

    i

    +

    2

    Q2+ 2Q2

    ie2i (

    )t/h

    = |I|2 + iQ2

    1

    |I|

    2

    + iQ21

    e2i (

    )t/h

    + |I|2 e2i t/ht/2T

    ( + iQ2)( + iQ2),

    17@ Cf. the figure above.

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    THE THEORY OF SCATTERING 335

    b = |I|2

    ( + iQ2)( + iQ2) 1 + e2i t/ht/2T

    + + iQ2

    1 e2i ()t/h

    ,

    b = |I|2

    ( + iQ2)( + iQ2) e2i ()t/h + e2i t/ht/2T

    + + iQ2

    1 e2i ()t/h

    .

    Quantityc:

    c = ILQ2

    1 12/Q2 + 2Q2 +

    ILQ2

    1 e

    2i()t/h

    2/Q2 + 2Q2

    + IL

    2/Q2 + 2Q21

    2/Q2 + 2Q2

    e2it/h et/2T

    Q2 i

    Q2 i

    2

    Q2+ 2Q2 i

    +

    2

    Q2+ 2Q2 ie

    2i ()t/h

    =

    IL

    + iQ21

    IL

    + iQ21

    e2i ()t/h

    + IL e2i t/ht/2T

    ( + iQ2)( + iQ2).

    c = IL( + iQ2)( + iQ2)

    1 + e2i t/ht/2T

    + + iQ2

    1 e2i ()t/h

    .

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    336 E. MAJORANA: RESEARCH NOTES ON THEORETICAL PHYSICS

    = e2iEt/h W+ I

    + iQ2

    e2iEt/h e2i(E0k)t/h et/2T

    0

    I

    + iQ2 IW+ LW

    + iQ2 e2iEt/h

    1 e2i t/ht/2T

    d

    +I

    IW+ LW

    + iQ2 e2iEt/h

    1

    1 e2i()t/h

    d,

    = e2i Et/h W+ a e2i E0t/h 0

    +

    bW

    IW+ LW

    dW e2i Et/h,

    H = Ee2iEt/h

    W+ IWe2i E0t/h

    0+ a E0e2i E0t/h

    0

    +

    a e2i E0t/hIWWdW

    +

    a e2i E0t/hLWWdW

    +

    EbW

    IW+ LW

    e2i E

    t/hdW

    +Q2

    bWdW 0e2i Et/h,

    IW =I:

    a = 2ih

    e2iWt/hI+ Q2

    bWe

    2i Wt/hdW

    ,

    bW = 2ih

    e2i Wt/h a.

    = e2i Et/hW

    + I

    + iQ2

    e2iEt/h e2i(E0k)t/h et/2T

    0

    I + iQ2

    IW+ LW

    + iQ2

    e2i Et/h

    1 e2i t/ht/2T

    d

    + I

    + iQ2

    IW+ LW

    e

    2i Et/h

    1 e2i()t/h

    d.

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    THE THEORY OF SCATTERING 337

    = + ,

    = e2iEt/hW+ I

    + iQ2e2iEt/h 0

    I + iQ2

    IW+ LW

    e

    2iEt/h

    1 e2i ()t/h

    d,

    = I + iQ2

    e2i(E0k)t/h et/2T 0

    I + iQ2

    IW+ LW

    + iQ2

    e2i Et/h

    1 e2i t/ht/2T

    d.

    Appendix:Transforming a differential equation

    u +

    0+

    1r

    u +

    0+

    1r

    u= 0,

    = r

    k

    u.

    u = rk u,

    u = u

    k

    r

    ,

    u = u

    k

    r

    2+ u

    2

    2 +

    k

    r2

    = u

    2k

    r

    +

    k(k+ 1)

    r2

    .

    2 k

    r

    +

    k(k+ 1)

    r2

    + 0

    0 k

    r+

    1r

    k1

    r2 + 0+

    1r

    = 0,

    +

    0+

    1r 2 k

    r

    +

    0+

    1 k0r

    +k(k+ 1) k1

    r2

    = 0.

    k=1

    2; 1 = 2k,

    + 0 +

    0+

    1 k0r

    k(k 1)r2

    = 0.