Norman F. Ramsey

A Search for the Electric Dipole Moment of the Neutron

We report on a search for the electric dipole moment of the neutron. Using a magnetic resonance technique with stored ultra-cold neutrons we have measured the electric dipole moment of the neutron to be −(3±5)×10−26 e cm.

Spin Rotation Constant and Rotational Magnetic Moment of 13C16O

13C16O has been studied by the molecular‐beam magnetic‐resonance method in the high‐field limit. Two different spectra were observed. These correspond, first, to the reorientation of the carbon‐13 nuclear spin with respect to the external field H, and second, to the reorientation of the rotational angular momentum with respect to H. By analyzing these spectra with third‐order perturbation theory, it was found that the carbon‐13 spin–rotation constant c = − (32.59 ± 0.15) kHz, and that the rotational gyromagnetic ratio gJ = −(0.25691 ± 0.00020) nm. From this measurement of gJ and the known value of the molecular quadrupole moment, the anisotropy constant f of the susceptibility tensor has been determined. It was shown that f / H2 = + (38.9 ± 3.9) × 10−5Hz G−2. By combining the present results for c and gJ with Huos ab initio calculations of the ground‐state electronic properties of the molecule, the average carbon‐13 shielding constant σa and the mean diamagnetic susceptibility ξa have been evaluated. The...

Experiments with separated oscillatory fields and hydrogen masers

Descriptions are given of the methods of separated and successive oscillatory fields and of the atomic hydrogen maser. Their applications to the precision spectroscopy of atoms and molecules are discussed along with specific examples of fundamental measurements best made with such devices. The applications of these methods to atomic clocks are discussed. Cesium-separated oscillatory fields atomic beam clocks are accurate to 10-13, and hydrogen masers are stable for several hours to 10-15. A discussion is given of fundamental experiments that require highly stable clocks, such as long-base-line radio astronomy, precise measurement of pulsar frequencies and stabilities, tests of relativity theories, and accurate navigation both on the earth and in outer space.

PROTON-PROTON SCATTERING AT ENERGIES FROM 46 TO 147 Mev

The angular distribution of the differential cross section and polarization in proton-proton scattering have been measured at 147, 118, 95, and 66 Mev; at the highest energy the angular range was 4 to 112 (center of mass), while at the other energies the region considered fell between about 20 and 80 . In each case the differential cross section is a few percent higher at 40 than at 90 , in disagreement with the receat results of Taylor at Harwell. The angular distribution of Pd sigma /d OMEGA indicates the necessity for F-waves in describing the interaction at 147 Mev, although these are not required at the lower energies. Measurements of the polarization at 45 , taken at 10-Mev intervals between 46 and 147 Mev, yield results about 20% higher than predicted by Gammel and Thaler. (auth)

The molecular Zeeman and hyperfine spectra of LiH and LiD by molecular beam high resolution electric resonance

The molecular Zeeman spectra of LiH and LiD in the 1Σ ground electronic state have been measured in the first rotational state (J=1) and zeroth vibrational state (v=0) by molecular beam electronic resonance. By fitting the observed resonance lines of several different magnetic fields to an appropriate Hamiltonian, values for the rotational g factor (gJ), the anisotropies of the nuclear shieldings (σTH,σTLi), and the anisotropy of the molecular magnetic susceptibility (ξT) were measured. The results are In order to fit the observed magnetic field spectra, accurate values of the hyperfine constants were required. The hyperfine spectra of several (J, v) states of LiH and LiD were measured. The results are Numbers in parentheses are the uncertainties in the final figures.

A measurement of parity non-conserving neutron spin rotation in lead and tin☆

Abstract The rotation, φ PNC , of a neutron beam polarization vector due to parity non-conserving forces is observed in natural Pb and Sn targets. The following values for φ PNC / l in units of 10 −6 rad/cm are found: Pb: +(2.24 ± 0.33), and Sn: −(3.19 ± 0.40). A positive sign corresponds to a right-handed rotation of the neutron spin about its momentum.

Stark hyperfine structure of hydrogen bromide

The ν=0, J=1,2 hyperfine spectra of hydrogen bromide have been measured with a molecular beam electric resonance spectrometer at electric fields of 1500–3500 V/cm. The hyperfine structure parameters were determined for H 79.81Br and D 79.81Br. The quadrupole interaction ratios are The distance derivative of the electric field gradient at the site of the bromine nucleus was determined to be d (q/qe)/d ([R−Re]/Re) =1.556(3). The magnetic octupole interaction of the bromine nucleus was negligible ‖ewΩ‖<0.5 Hz. The electric polarizability anisotropy was measured to be (α∥−α⊥) =0.37(9) A3. The same technique was used for DCl with the result (α∥−α⊥) = 0.23(3) A3. Numbers in parenthesis are uncertainties in the final figures.

Rotational magnetic moment spectra of a series of tetrahedral molecules

The molecular beammagnetic resonance method has been used to study the rotational magnetic momentspectrum of each of a series of tetrahedral XY4 molecules in which nucleus X has no spin and nucleus Y has a spin of one‐half. The transitions observed involve the reorientation of the rotational angular momentum relative to an external magnetic field in the high‐field limit. It is shown that to excellent approximation the transition frequencies depend on only two molecular constants: the rotational g factorg J and the average spin rotation constantc a of nucleus Y. For each molecule, both constants were determined. The results are for CH4 g J =+0.31338(4) nm, c a =+10.5(5) kHz; for SiH4 g J =−0.27036(50) nm, c a =+3.6(6) kHz; for GeH4 g J =−0.10815(14) nm, c a =+4.0(3) kHz; for CF4 g J =−0.03124(5) nm, c a =−6.78(6) kHz; for SiF4 g J =−0.03193(4) nm, c a =−2.45(8) kHz; for GeF4 g J =−0.02658(5) nm, c a =−1.85(5) kHz. For each tetrafluoride, the sign of c a was taken from earlier theoretical work; all other signs were determined experimentally here. In all cases where comparison values are available, the agreement is good. The application of these measurements to investigations of molecular electronic properties and of nuclear spin relaxation processes is discussed.

Dipole moments and spin rotations of the neutron

Abstract A recently completed neutron beam experiment is described which sets the limit on μE the neutron electric dipole moment of | μ E e | −24 cm . A new experiment with bottled cold neutrons has been started and should eventually provide much lower limit. The original apparatus has recently been used to measure the ratio gm n μ p of the magnetic moment of the neutron to that of proton with the result μ n μ p = −0.68497945(17) . A new apparatus is being planned to measure the parity violating small rotation of the neutron spin due to the weak interaction when the neutron passes through a material such as Bi or Sn. A still larger rotation may be studied when the molecules of the medium are optically active (cork screw shaped).

Low‐Field Hyperfine Spectrum of CH4

The hyperfine spectrum of CH4 has been observed in the low field limit by the molecular‐beam magnetic‐resonance method. Ten partially resolved lines were observed in the frequency region below 100 kHz. The lines associated with the nuclear quintet were found to be equally spaced with frequencies which depend only on the average spin‐rotation constant ca. The lines associated with the nuclear triplet were found to form a complex spectrum with frequencies which depend not only on ca, but also on the anisotropy in the spin rotation matrix cd and on the tensor spin—spin coupling constant d. In the analysis of the triplet spectrum, the energies of the tensor interactions have been calculated in detail by applying the recent group theoretical treatment of Yi, Ozier, and Anderson. It was determined that ca = + (10.4 ± 0.1) kHz; cd = + (18.5 ± 0.5) kHz and d = + (20.9 ± 0.3) kHz. For these values, the calculated and experimental frequencies agree to within a rms deviation of 350 Hz.