Monte Carlo Model of Charge Recombination in Feldspars

potential barrier penetration constant

4 

9

10

-1

m

9 

9

10

-1

m

tunneling frequency

13

10

Hz

14

10

Hz

15

10

Hz

length of side of cell

50 nm

75 nm

100 nm

number of cells

10

20

50

Feldspars (aluminosilicates of potassium, sodium and calcium) are very common geological materials that emit light when heated or after exposure to visible or infrared radiation. These processes can occur in nature. Two different modes of light emission are thermoluminescence (TL) and optically stimulated luminescence (OSL). When feldspars are irradiated, separation of charge can occur, creating closely spaced electron-hole pairs. These pairs can recombine to emit light by quantum tunneling.

The study of how these electron-hole pairs recombine over geological times can be applied to luminescence dating and luminescence dosimetry.

This Demonstration uses Monte Carlo methods to simulate the recombination process, taking account of the physical parameters that characterize feldspar crystals. We model 10 electron-hole pairs located at random positions in a cube. The plot shows how these pairs recombine in the natural crystal over millions of years. The tunneling process is very slow and takes place over geological timescales. The horizontal error bars are the standard deviation of

N

Monte Carlo computations, where

N=10,20,50

. The horizontal axis represents the elapsed geological time.