▁by ▁these ▁react ing ▁with ▁water ▁and ▁sul f ide : ▁Production ▁of ▁an ▁electron ▁hole ▁pair ▁C d S   + ▁h ν   → ▁e −   + ▁hole + ▁ ▁Re action ▁of ▁electron ▁ 2 e −   + ▁ 2 H 2 O   → ▁H 2   + ▁ 2 OH − ▁Re action ▁of ▁hole ▁ 2 hole +   + ▁S 2 − ▁→ ▁S ▁ ▁Str ucture ▁and ▁physical ▁properties ▁Cad m ium ▁sul f ide ▁has , ▁like ▁z inc ▁sul f ide , ▁two ▁cry stal ▁forms . ▁The ▁more ▁stable ▁hex ag onal ▁wur tz ite ▁structure ▁( found ▁in ▁the ▁min eral ▁Green ock ite ) ▁and ▁the ▁cub ic ▁z inc ▁bl ende ▁structure ▁( found ▁in ▁the ▁min eral ▁Haw ley ite ). ▁In ▁both ▁of ▁these ▁forms ▁the ▁cad m ium ▁and ▁sul fur ▁atoms ▁are ▁four ▁coordinate . ▁There ▁is ▁also ▁a ▁high ▁pressure ▁form ▁with ▁the ▁Na Cl ▁rock ▁salt ▁structure . ▁ ▁Cad m ium ▁sul f ide ▁is ▁a ▁direct ▁band ▁gap ▁sem icon duct or ▁( g ap ▁ 2 . 4 2 ▁e V ). ▁The ▁proxim ity ▁of ▁its ▁band ▁gap ▁to ▁visible ▁light ▁w avel ength s ▁gives ▁it ▁a ▁col oured ▁appearance . ▁As ▁well ▁as ▁this ▁obvious ▁property ▁other ▁properties ▁result : ▁the ▁conduct ivity ▁increases ▁when ▁ir rad i ated , ▁( leading ▁to ▁uses ▁as ▁a ▁phot ores istor ) ▁when ▁combined ▁with ▁a ▁p