Introdution

Here is a full numerical calculation of the time-of-flight distribution for a 1 field or 2 field mass spectrometer. The trajectories of the particles are calculated by solving the classical motion equation of charged particles with a 4rth order Runge-Kutta algorithm. It can be used as initial condition an isotropic distribution of particles emitted in space. The mother ion is defined by its lifetime and its initial kinetic energy distribution. The daughter ion is assumed to be emitted with an isotropic distribution and we considered the case of variable release kinetic energy in the dissociation. The final time of flight is constructed with Monte-Carlo integration. To understand the result of the simulation two cases ought to be considered. If the mother ion dissociate in the drift tube the daughter ion arrive at the time of flight of the mother ion. The peak is symmetric and the time spread is related to kinetic energy imparted to the daughter ion, the fields strength as well as the length of the drift tube. If the mother ion dissociation happens before the drift tube, the daughter ion arrive with a short time of flight . The peak is asymmetric and looks like an exponential decay which actually follows the dissociation rate. The peak shape is in that case independent of the extraction condition as well as the kinetic energy but depends on the ratio of the masses.

Code

• Windows XOP

Use

• Intialization

SpectroParam(E_extr, L_extr, E_acc, L_acc, E_drift, L_drift)

• E_extr: electric field in the extraction region
• L_extr: length of the extraction region
• E_acc: electric field in the acceleration region
• L_acc: length of the acceleration region
• E_drift: electric field in the drift tube
• L_drift: length of the drift tube

ParticlesParam(m_m, c_m, KE_m, l_m, beta_m, m_d, c_d, KE_d, beta_d)

• m_m: mother ion mass (a.u.)
• c_m: mother ion charge (+/-q)
• KE_m: Kinetic energy distribution of the mother ion (eV)
• l_m: lifetime_mother (ns)
• beta_m: not implement (=0)
• m_d: mother ion mass (a.u.)
• c_d: daughter ion charge (+/-q)
• KE_d:Kinetic energy released in the dissociation (eV)
• beta_d:not implement (=0)

• Execution

CalculTrajectories(mode, dt_m, nb_i, dt_d, nb_d, dt_dm)

• mode: 0-> only calcul mother ion TOF, 1-> mother and daughter ion TOFs
• dt_m: (Runge Kunta) integration step for mother ion calcul (ps)
• nb_i: (Monter-Carlo) number of iteration for angular distribution on the daughter ion
• dt_d: (Runge Kunta) integration step for mother ion calcul (ps)
• nb_d: (Monter-Carlo) number of iteration for angular distribution on the daughter ion
• dt_dm: every

Here we give the example… coucou

Last edited by Mathieu Gisselbrecht at Oct 11, 2006 10:50 AM - Edit content - View source