There are several smells that can repel rats, but none of them can kill rats instantly. Here are some smells that can deter rats:

• Peppermint oil: Rats have a highly developed sense of smell, and peppermint oil is offensive to them. To use peppermint oil as a repellent, soak a cotton ball with 25-30 drops of peppermint essential oil and place it in areas where rats are commonly found.

• Mothballs: Mothballs can be placed in areas where rats are commonly found. However, they should not be touched with bare hands or positioned around the room.

• Ammonia: Ammonia can be mixed with water and detergent and placed in a bowl near rats. The smell of ammonia is very pungent and can repel rats.

• Eucalyptus oil: The smell of eucalyptus oil can repel rats because it smells like death to them.

• Cayenne pepper: The smell of cayenne pepper can repel rats because it smells like predators to them. Rats will find an exit very fast and leave without hesitation when you use cayenne pepper or hot sauce.

Its important to note that while these smells can deter rats, they are not a guaranteed solution and may need to be reapplied regularly. Additionally, none of these smells can kill rats instantly.