TY - JOUR

T1 - Separation of chemical elements in the atmospheres of CP stars under the action of light induced drift

AU - Parkhomenko, A. I.

AU - Shalagin, A. M.

PY - 2017/11/1

Y1 - 2017/11/1

N2 - A mechanism for the separation of chemical elements and isotopes in the atmospheres of chemically peculiar (CP) stars due to light-induced drift (LID) of ions is discussed. The efficiency of separation due to LID is proportional to the relative difference of the transport frequencies for collisions of ions of heavy elements located in the excited state (collision frequency νe) and ground state (collision frequency νg) with neutral buffer particles (hydrogen and helium), (νe − νg)/νg. The known interaction potentials are used to numerically compute the relative difference (νe H − νg H)/νg H for collisions between the ions Be+, Mg+, Ca+, Sr+, Cd+, Ba+, Al+, and C+ and hydrogen atoms. These computations show that, at the temperatures characteristic of the atmospheres of CP stars, T = 7000−20 000 K, values of |νe H −νg H |/νg H ≈ 0.1−0.4 are obtained. With such relative differences in the transport collision frequencies, the LID rate of ions in the atmospheres of coolCP stars (T < 10000 K) can reach ~0.1 cm/s,which exceeds the drift rate due to light pressure by an order of magnitude. This means that, under these conditions, the separation of chemical elements under the action of LID of ions could be an order of magnitude more efficient than separation due to light pressure. Roughly the same manifestations of LID and light pressure are also expected in the atmospheres of hotter stars (20 000 > T > 10 000 K). LID of heavy ions is manifest only weakly in very hot stars (T > 20 000 K).

AB - A mechanism for the separation of chemical elements and isotopes in the atmospheres of chemically peculiar (CP) stars due to light-induced drift (LID) of ions is discussed. The efficiency of separation due to LID is proportional to the relative difference of the transport frequencies for collisions of ions of heavy elements located in the excited state (collision frequency νe) and ground state (collision frequency νg) with neutral buffer particles (hydrogen and helium), (νe − νg)/νg. The known interaction potentials are used to numerically compute the relative difference (νe H − νg H)/νg H for collisions between the ions Be+, Mg+, Ca+, Sr+, Cd+, Ba+, Al+, and C+ and hydrogen atoms. These computations show that, at the temperatures characteristic of the atmospheres of CP stars, T = 7000−20 000 K, values of |νe H −νg H |/νg H ≈ 0.1−0.4 are obtained. With such relative differences in the transport collision frequencies, the LID rate of ions in the atmospheres of coolCP stars (T < 10000 K) can reach ~0.1 cm/s,which exceeds the drift rate due to light pressure by an order of magnitude. This means that, under these conditions, the separation of chemical elements under the action of LID of ions could be an order of magnitude more efficient than separation due to light pressure. Roughly the same manifestations of LID and light pressure are also expected in the atmospheres of hotter stars (20 000 > T > 10 000 K). LID of heavy ions is manifest only weakly in very hot stars (T > 20 000 K).

KW - LYING ELECTRONIC STATES

KW - POTENTIAL-ENERGY CURVES

KW - AB-INITIO

KW - STELLAR ATMOSPHERES

KW - INDUCED DIFFUSION

KW - EXCITED-STATES

KW - ISOTOPES

KW - ATOMS

UR - http://www.scopus.com/inward/record.url?scp=85035095682&partnerID=8YFLogxK

U2 - 10.1134/S1063772917110038

DO - 10.1134/S1063772917110038

M3 - Article

AN - SCOPUS:85035095682

VL - 61

SP - 974

EP - 982

JO - Astronomy Reports

JF - Astronomy Reports

SN - 1063-7729

IS - 11

ER -