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// $Id: G4VGammaDeexcitation.cc,v 1.20 2010/11/17 19:17:17 vnivanch Exp $
// GEANT4 tag $Name: geant4-09-04-ref-00 $
//
// -------------------------------------------------------------------
//      GEANT 4 class file 
//
//      CERN, Geneva, Switzerland
//
//      File name:     G4VGammaDeexcitation
//
//      Author:        Maria Grazia Pia (pia@genova.infn.it)
// 
//      Creation date: 23 October 1998
//
//      Modifications: 
//
//        21 Nov 2001, Fan Lei (flei@space.qinetiq.com)
//           Modified GenerateGamma() and UpdateUncleus() for implementation
//           of Internal Conversion processs 
//      
//        15 April 1999, Alessandro Brunengo (Alessandro.Brunengo@ge.infn.it)
//              Added creation time evaluation for products of evaporation
//
//        19 April 2010, J. M. Quesada calculations in CM system
//              pending final boost to lab system  (not critical)
//
//        23 April 2010, V.Ivanchenko rewite kinematic part using PDG formula
//                                    for 2-body decay
//
// -------------------------------------------------------------------

#include "G4VGammaDeexcitation.hh"

#include "globals.hh"
#include "Randomize.hh"
#include "G4Gamma.hh"
#include "G4Electron.hh"
#include "G4LorentzVector.hh"
#include "G4VGammaTransition.hh"
#include "G4Fragment.hh"
#include "G4FragmentVector.hh"

#include "G4ParticleTable.hh"
#include "G4IonTable.hh"

#include "G4DiscreteGammaTransition.hh"


G4VGammaDeexcitation::G4VGammaDeexcitation(): _transition(0), _verbose(0),
					      _electronO (0), _vSN(-1)
{ 
  _nucleus = 0;
}

G4VGammaDeexcitation::~G4VGammaDeexcitation()
{ 
  if (_transition != 0) { delete _transition; }
}

G4FragmentVector* G4VGammaDeexcitation::DoTransition()
{
  Initialize();
  G4FragmentVector* products = new G4FragmentVector();
 
  if (CanDoTransition())
    {
      G4Fragment* gamma = GenerateGamma();
      if (gamma != 0) { products->push_back(gamma); }
    }
 
  if (_verbose > 1) {
    G4cout << "G4VGammaDeexcitation::DoTransition - Transition deleted " << G4endl;
  }
 
  return products;
}

G4FragmentVector* G4VGammaDeexcitation::DoChain()
{
  if (_verbose > 1) { G4cout << "G4VGammaDeexcitation::DoChain" << G4endl; }
  const G4double tolerance = CLHEP::keV;

  Initialize();
  G4FragmentVector* products = new G4FragmentVector();
  
  while (CanDoTransition())
    {      
      _transition->SetEnergyFrom(_nucleus->GetExcitationEnergy());
      G4Fragment* gamma = GenerateGamma();
      if (gamma != 0) 
	{
	  products->push_back(gamma);
	  //G4cout << "Eex(keV)= " << _nucleus->GetExcitationEnergy()/keV << G4endl;
	  if(_nucleus->GetExcitationEnergy() <= tolerance) { break; }
	  Update();
	}
    } 
  
  if (_verbose > 1) {
    G4cout << "G4VGammaDeexcitation::DoChain - Transition deleted, end of chain " << G4endl;
  }
  
  return products;
}

G4Fragment* G4VGammaDeexcitation::GenerateGamma()
{
  // 23/04/10 V.Ivanchenko rewrite complitely
  G4double eGamma = 0.;
  
  if (_transition != 0) {
    _transition->SelectGamma();  // it can be conversion electron too
    eGamma = _transition->GetGammaEnergy(); 
    if(eGamma <= 0.0) { return 0; }
  }
  G4double excitation = _nucleus->GetExcitationEnergy() - eGamma;
  if(excitation < 0.0) { excitation = 0.0; } 
  if (_verbose > 1 && _transition != 0 ) 
    {
      G4cout << "G4VGammaDeexcitation::GenerateGamma - Edeexc(MeV)= " << eGamma 
	     << " ** left Eexc(MeV)= " << excitation
	     << G4endl;
    }
  
  // Do complete Lorentz computation 

  G4LorentzVector lv = _nucleus->GetMomentum();
  G4double Mass = _nucleus->GetGroundStateMass() + excitation;

  // select secondary
  G4ParticleDefinition* gamma = G4Gamma::Gamma();

  G4DiscreteGammaTransition* dtransition = 
    dynamic_cast <G4DiscreteGammaTransition*> (_transition);
  if ( dtransition && !( dtransition->IsAGamma()) ) { 
    gamma = G4Electron::Electron(); 
    _vSN = dtransition->GetOrbitNumber();   
    _electronO.RemoveElectron(_vSN);
    lv += G4LorentzVector(0.0,0.0,0.0,CLHEP::electron_mass_c2 - dtransition->GetBondEnergy());
  }

  // check consistency  
  G4double eMass = gamma->GetPDGMass();

  G4double Ecm       = lv.mag();
  G4ThreeVector bst  = lv.boostVector();

  G4double GammaEnergy = 0.5*((Ecm - Mass)*(Ecm + Mass) + eMass*eMass)/Ecm;
  if(GammaEnergy <= eMass) { return 0; }

  G4double cosTheta = 1. - 2. * G4UniformRand(); 
  G4double sinTheta = std::sqrt(1. - cosTheta * cosTheta);
  G4double phi = twopi * G4UniformRand();
  G4double mom = std::sqrt((GammaEnergy - eMass)*(GammaEnergy + eMass));
  G4LorentzVector Gamma4P(mom * sinTheta * std::cos(phi),
			  mom * sinTheta * std::sin(phi),
			  mom * cosTheta,
			  GammaEnergy);
  Gamma4P.boost(bst);  
  G4Fragment * thePhoton = new G4Fragment(Gamma4P,gamma);

  G4double gammaTime = _nucleus->GetCreationTime() + _transition->GetGammaCreationTime();
  thePhoton->SetCreationTime(gammaTime);

  lv -= Gamma4P;
  _nucleus->SetMomentum(lv);
  _nucleus->SetCreationTime(gammaTime);

  //G4cout << "G4VGammaDeexcitation::GenerateGamma left nucleus: " << _nucleus << G4endl;
  return thePhoton;
}

void G4VGammaDeexcitation::Update()
{
  if (_transition !=  0) 
    { 
      delete _transition;
      _transition = 0;
      if (_verbose > 1) {
	G4cout << "G4VGammaDeexcitation::Update - Transition deleted " << G4endl;
      }
    }
  
  _transition = CreateTransition();
  if (_transition != 0) 
    {
      _transition->SetEnergyFrom(_nucleus->GetExcitationEnergy());
      // if ( _vSN != -1) (dynamic_cast <G4DiscreteGammaTransition*> (_transition))->SetICM(false);
      // the above line is commented out for bug fix #952. It was intruduced for reason that
      // the k-shell electron is most likely one to be kicked out and there is no time for 
      // the atom to deexcite before the next IC. But this limitation is causing other problems as 
      // reported in #952
    }
  
  return;
}