Lifetime of the surface magnetoplasmons in metallic nanoparticles

We study the influence of an external magnetic field on the collective electronic excitations in metallic nanoparticles. While the usual surface plasmon corresponding to the collective oscillation of the electrons with respect to the ionic background persists in the direction parallel to the magnetic field, the components in the perpendicular plane are affected by the field and give rise to two collective modes with field-dependent frequencies, the surface magnetoplasmons. We analyze the decay of these collective excitations by their coupling to particle-hole excitations and determine how their lifetimes are modified by the magnetic field. In particular, we show that the lifetime of the usual surface plasmon is not modified by the magnetic field, while the lifetime of the two surface magnetoplasmons present a weak magnetic-field dependence. Optical spectroscopy experiments are suggested in which signatures of the surface magnetoplasmons may be observed.Comment: 11 pages, 6 figures; published versio

Friction of the surface plasmon by high-energy particle-hole pairs: Are memory effects important?

We show that the dynamics of the surface plasmon in metallic nanoparticles damped by its interaction with particle-hole excitations can be modelled by a single degree of freedom coupled to an environment. In this approach, the fast decrease of the dipole matrix elements that couple the plasmon to particle-hole pairs with the energy of the excitation allows a separation of the Hilbert space into low- and high-energy subspaces at a characteristic energy that we estimate. A picture of the spectrum consisting of a collective excitation built from low-energy excitations which interacts with high-energy particle-hole states can be formalised. The high-energy excitations yield an approximate description of a dissipative environment (or "bath") within a finite confined system. Estimates for the relevant timescales establish the Markovian character of the bath dynamics with respect to the surface plasmon evolution for nanoparticles with a radius larger than about 1 nm.Comment: 8 pages, 1 figure; see also cond-mat/070372

The Effect of the Sperry Messenger Fuselage on the Air Flow at the Propeller Plane

In order to study the effect of the fuselage, landing gear, and engine on the air flow through the propeller, a survey was made in the plane of the Sperry Messenger propeller with the propeller removed. The tests were made in the 20-foot air stream of the propeller research tunnel of the National Advisory Committee for Aeronautics at Langley Field, Virginia. The variation of the velocity with distance from the center in the propeller plane was found to be appreciable and well worth consideration in the design of propellers. It was also found that the velocity through the propeller plane was affected by the presence of the engine, and that the velocity in front of the landing gear was lower than that at other points in the propeller plane having the same radius

Navy propeller section characteristics as used in propeller design

This report contains artificial aerodynamic characteristics of a set of propeller sections to be used in designing propellers by means of the blade element theory. Characteristics computed from model propeller tests for a single section are extended to cover sections of Navy propeller sections at high Reynolds Number in the variable density tunnel of the NACA

The Drag of a J-5 Radial Air-Cooled Engine

This note describes tests of the drag due to a Wright "Whirlwind" (J-5) radial air-cooled engine mounted on a cabin type airplane. The tests were made in the 20-foot Propeller Research Tunnel of the National Advisory Committee for Aeronautics. The drag was obtained with three different types of exhaust stacks: Short individual stacks, a circular cross section collector ring, and a streamline cross section collector ring

Full Scale Investigation of the Drag of a Wing Radiator

Tests were made on the 1927 Williams racer in order to determine the effect of the wing radiator on the airfoil characteristics. It was found that the radiator doubled the minimum drag of the portion of the wing it covered, and also reduced the lift somewhat

Study of open jet wind tunnel cones

Tests have been made by the National Advisory Committee for Aeronautics on the air flow in an open jet wind tunnel with various sizes, shapes, and spacings of cones, and the flow studied by means of velocity and direction surveys in conjunction with flow pictures. It was found that for all combinations of cones tested the flow is essentially the same, consisting of an inner core of decreasing diameter having uniform velocity and direction, and a boundary layer of more or less turbulent air increasing in thickness with length of jet. The energy ratio of the tunnel was obtained for the different combinations of cones, and the spilling around the exit cone causing undesirable air currents in the experiment chamber was noted. An empirical formula is given for the design of cones having no appreciable spilling

Propeller design: extension of test data on a family of model propellers by means of the modified blade element theory II

This report is the second of a series of four on propeller design, and describes the method used to extend the data obtained from tests on a family of thirteen model propellers to include all propellers of the same form likely to be met in practice. This necessitates the development of a method of propeller analysis which when used to calculate the powers and efficiencies gives results which check the tests throughout their range

Propeller scale effect and body interference

This note shows that the main part of the discrepancy between full flight propeller performance and the performance of models in a wind tunnel is due to a scale effect, and that a minor part is caused by body interference. Analyses are made of propeller performances on several standard airplanes, and the actual brake horsepower compared with the power as calculated from model test data. The calculated power is based on that absorbed by a wind tunnel propeller model which is geometrically similar to the full scale propeller and is operating under the same ratio of V/nD

A Comparison of Propeller and Centrifugal Fans for Circulating the Air in a Wind Tunnel

The tests described in this paper afford a direct comparison of the efficiency and smoothness of flow obtained with propeller fan and multiblade centrifugal fan drives in the same wind tunnel. The propeller fan was found to be superior to the centrifugal fan in that the efficiency was about twice as great, and the flow much smoother