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Blue light stimulated luminescence (BLSL); moonlight bleaching; daylight bleaching; luminescence dating.

Moonlight is sunlight reflected from the moon’s surface. It is additionally modulated by the Earth’s atmosphere, dust and pollutants on its way to the surface of the Earth. This contribution reports the bleaching rates of blue light stimulated luminescence (BLSL) signal of Quartz under full moonlight exposure at the Earth’s surface. Quartz BLSL reduced to 70% by an exposure of 5 hrs moonlight, is in contrast to $\sim$90% reduction in < 3 s with daylight. This was anticipated due to (a) reduced moonlight flux by about a factor of half a million (Agrawal in Lat. Am. J. Phys. Educ. 4(2):325–328, 2010; J. Phys. Astron. 5(1):1–15, 2017); (b) inverse power law dependence of bleaching efficiency on wavelength (Spooner in The validity of optical dating based on feldspar, Ph.D. Thesis, Oxford University, Oxford, 1993; Chen and McKeever in Theory of Thermoluminescence and related phenomena, World Scientific Publications, London, 1997, Chen and Pagonis in Thermally and optically stimulated luminescence: A simulation approach, Wiley and Sons, Chichester, 2011); and (c) moonlight and daylight have spectral peaks around 650 and 550 nm, respectively. Deconvolution of OSL components suggests that moonlight affects the fast component of OSL signal the most. This has ramification for the application in polar regions, where the availability of daylight is at a premium during the winter months. Within a given context, it is conjectured that this could be used to infer the seasonality of sediment transport.

$\bf{Highlights}$

$\bullet$ Up to 40% reduction of quartz luminescence signal observed over long moonlight exposure.

$\bullet$ Moonlight can bleach up to 70% of the fast component of blue light stimulated luminescence signal.

$\bullet$ Moonlight bleaching may hamper the accuracy of ages of sediments which are only transported during night.

$\bullet$ Seasonality of sediment deposition can be studied using the bleaching effect of moonlight on quartz.

RAJAPARA H M^{1 2} VINAYAK KUMAR¹ NAVEEN CHAUHAN¹ GAJJAR P N² SINGHV A K¹

1. AMO-PH Division, Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, India.
2. Department of Physics, Electronics and Space Science, University School of Sciences, Gujarat University, Ahmedabad 380 009, India.

Published

15 October 2020

Manuscript received

13 December 2019

Manuscript revised

27 June 2020

Accepted

9 July 2020

Final version published online

15 October 2020