Abstract The influence of Van der Waals forces on the lifetime of coherently excited hyperfine‐states |FimFi〉 and |FimFi〉 of alkalilike atoms i by collissions with inert gas atoms j in the groundstate |FjmFi〉 has been examined. To do this the timedependent Schrödinger equation has been solved on taking into account a static magnetic field, a radiation field and a Van der Waals force. Introducing an impact parameter model for the colliding atoms with small scattering angles which form a quasimolecule |μ〉 = |FimFiFjmFi 〉 an expression for the cross section σμμ has been derived which determines the halfwidth Γ μμ of the coherently excited states. On making use of the irreducible tensor representation the calculation of the cross‐section has been reduced to the calculation of multipole transitions. The result has been applied e. g. to the coherently excited 3d104p2P3/2‐states of Cu I colliding by dipole‐dipole interaction with inert gas atoms He I, and Ar I in the ground state. The values agree well with data which have been derived from zero‐level‐crossing experiments.
The admixture effect of dipole and quadrupole type atomic transitions on the Stokes parameters characterizing the emitted radiation in the presence of an external magnetic field is studied. The transition from an upper level with angular momentum Ju = 3/2 to a lower level with angular momentum Jl = 1/2 is considered to take account of the admixture effect. The analytical expressions showing the emitted Stokes parameters for the case of upper and lower levels having same parities are derived. It is shown that the radiative transition probabilities of magnetic dipole (M1) and electric quadrupole transition (E2) are more intense than those of electric dipole transition (E1) and magnetic quadrupole transition (M2). The polarization components that are not usually seen in the Stokes I; Q and V profiles appear due to the admixture effect. The interference of the polarization components with opposite signs is responsible for the smaller strength of Stokes I; Q; V in admixture transition compared to those observed in pure transition. In pure dipole transition case, U Stokes profile is always zero for all emitted radiation directions. However, the Stokes U profile arises only due to the admixture effect.
The hyperfine structure of transitions in the three-step scheme 5d6s22D3/2–5d6s6p4F
5/2∘ –5d6s7s4D3/2– (53 375 cm–1)
1/2∘ of lutetium ionization is studied for 175Lu, 176Lu, and 177Lu isotopes using the photoionization laser spectroscopy method. Values of the magnetic dipole (A) and electric quadrupole (B) interaction constants are determined, as well as the energies, the isotope shifts, and the radiative lifetimes for the 5d6s7s4D3/2 and (53 375 cm–1)
1/2∘ levels.