. (2012). Quasielastic scattering in the interaction of ultracold neutrons with a liquid wall and application in a reanalysis of the Mambo I neutron-lifetime experiment. We develop a theory of ultracold and very cold neutron scattering on viscoelastic surface waves up to second-order perturbation theory. The results are applied to reanalyze the 1989 neutron-lifetime experiment using ultracold neutron storage in a Fomblin-coated vessel by Mampe et al. [Phys. Rev. Lett. 63, 593 (1989)]. Inclusion of this theory of the quasielastic scattering process in the data analysis shifts the neutron lifetime value from 887.6 ± 3 to 882.5 ± 2.1 s.

We analyze the depolarization of ultracold neutrons confined in a magnetic field configuration similar to those used in existing or proposed magnetogravitational storage experiments aiming at a precise measurement of the neutron lifetime. We use an extension of the semiclassical Majorana approach as well as an approximate quantum mechanical analysis, both pioneered by Walstrom et al. [Nucl. Instrum. Methods Phys. Res. A 599, 82 (2009)]. In contrast with this previous work we do not restrict the analysis to purely vertical modes of neutron motion. The lateral motion is shown to cause the predominant depolarization loss in a magnetic storage trap. The system studied also allowed us to estimate the depolarization loss suffered by ultracold neutrons totally reflected on a nonmagnetic mirror immersed in a magnetic field. This problem is of preeminent importance in polarized neutron decay studies such as the measurement of the asymmetry parameter A using ultracold neutrons, and it may limit the efficiency of ultracold neutron polarizers based on passage through a high magnetic field.

Pendlebury et al. [Phys. Rev. A 70, 032102 (2004)] were the first to investigate the role of geometric phases in searches for an electric dipole moment (EDM) of elementary particles based on Ramsey-separated oscillatory field magnetic resonance with trapped ultracold neutrons and comagnetometer atoms. Their work was based on the Bloch equation and later work using the density matrix corroborated the results and extended the scope to describe the dynamics of spins in general fields and in bounded geometries. We solve the Schrödinger equation directly for cylindrical trap geometry and obtain a full description of EDM-relevant spin behavior in general fields, including the short-time transients and vertical spin oscillation in the entire range of particle velocities. We apply this method to general macroscopic fields and to the field of a microscopic magnetic dipole.

A new modified Morse potential is introduced to describe the vibrational motion of diatomic molecules. The vibrational energy eigenvalues for the ground state of the H2 and N2 molecules are obtained by numerically solving the time-independent Schrödinger equation using a Python program and the Matrix Numerov method for the case of the Morse potential, Hulbert-Hirschfelder potential, and the modified Morse potential functions. The comparison of the vibrational energy eigenvalues and the anharmonicity constant obtained for the modified Morse potential function reveals better agreement with the experimental data than the other potential functions. Also, the proposed modified Morse potential function fits the RKR potential energy curve more closely than the Morse potential function and Hulbert-Hirschfelder potential function, especially in the region where the potential extends to near the dissociation limit.

We review the diffuse scattering and the loss coefficient in ultracold neutron reflection from slightly rough surfaces, report a surprising reduction in loss coefficient due to roughness, and discuss the possibility of transition from quantum treatment to ray optics. The results are used in a computer simulation of neutron storage in a recent neutron lifetime experiment that reported a large discrepancy of neutron lifetime with the current particle data value. Our partial reanalysis suggests the possibility of systematic effects that were not included in this publication.