"an atomic clock based on the energy difference between two states of the caesium nucleus in a magnetic field"@en-us . "caesium clock"^^ . "102365974"@en-us . . "02935490-n"^^ . . "102831157"@en-us . . . . . "caesium clock"@en-us . . "102935490"^^ . . "0"^^ . "0"^^ .