Patent ID: 8907276

Claim:
A method for measuring the population of atoms in a vapor cell, the method comprising: collecting a sample of atoms from the vapor cell; applying radio frequency (RF) spectroscopy to the sample of atoms during a first time period such that a first portion of the atoms are in an upper ground state and a second portion of the atoms are in a lower ground state; applying light to the sample of atoms after the RF spectroscopy is applied to produce a first fluorescence of the atoms such that the atoms in the sample are left in the lower ground state; measuring a population of the atoms in the upper ground state based on the first fluorescence of the atoms; applying a timed RF pulse to the sample of atoms during a second time period to transfer the atoms in the sample that are left in the lower ground state to the upper ground state, wherein there is a third time period, between the first time period and the second time period, during which an RF field is not applied; applying light to the sample of atoms after the timed RF pulse is applied to produce a second fluorescence of the atoms; and measuring a population of the atoms in the sample based on the second fluorescence of the atoms.