Short-term frequency stabilization of diode-laser-pumped Nd:YAG lasers using double-pendulum suspended cavities

We describe the improvement of short-term frequency stability of diode-laser-pumped Nd:YAG lasers. To improve the vibrational isolation of reference cavities, the reference cavities were suspended by a double pendulum with magnetic damping. The frequency noise was reduced to lower than 1 Hz/Hz at Fourier frequencies higher than 5 Hz and the minimum noise of 7 × 10^–3 Hz/Hz was recorded. The minimum root Allan variance was about 10^–14 for the sampling time of 0.01 s. Heating of the reference cavity by absorbed laser power caused the thermal drift of cavity resonance frequencies. It resulted in the laser linewidth in the range of 30–50 Hz.     

Dipolar relaxation in an ultra-cold gas of magnetically trapped chromium atoms

We investigate, both theoretically and experimentally, dipolar relaxation in a gas of magnetically trapped chromium atoms. We find that the large magnetic moment of 6_B results in an event rate coefficient for dipolar relaxation processes of up to 3.2×10^-11 cm³s^-1 in a magnetic field of 44 G. We present a theoretical model based on pure dipolar coupling, which predicts dipolar relaxation rates that agree with our experimental observations. This very general approach can be applied to a large variety of dipolar gases. PACS 34.50.-s; 34.50.PI; 03.65.NK; 32.80.PJ     

Pyroelectric detection of a CO2 laser beam using organic copolymers

Pyroelectric detection of a CO₂ laser beam has been investigated by using organic copolymers such as VDF/TrFE- and VDCN/VAc copolymers, and compared with that of PVDF polymer. The voltage responsitiviesR _v are 40 mV/W for VDF/TrFE and 2 mV/W for VDCN/VAc at room temperature and at a chopping frequency of 200 Hz. (For comparison, the value of PVDF is 20 mV/W.) From the frequency dependence of the detected output, the electric time constant _E is evaluated to be about 6.4 ms and 2.6 ms for the former and latter copolymers with the detection area 3×3 mm², respectively. Some theoretical discussion is also given of the responsivity, frequency dependence and temperature dependence obtained.     

Die dreidimensionale Stabilisierung von Ladungsträgern in einem Vierpolfeld

It is shown that particles of a specific chargee/m are confined in three dimensions by a high frequency electric quadrupole field with the potential?=c · U(t)· (x ²+y ²?2z ²). The confinement is mass selective. The theoretical predictions are verified by experiments with ions of different masses and with electrons. The mass selection, maximum number of stored charges and their mean life time in the field are measured. Furthermore the influence of a magnetic field on the motion of the charges is investigated.     

The magnetic hyperfine field of bromine in iron by NMR/ON

Nuclear magnetic resonance of⁸²Br oriented at low temperature in iron has been observed with a sample prepared by ion implantation atT<0.2 K. The asymmetric resonance signal can be decomposed in a broad background signal and a narrow line of FWHM=1.8 (4) MHz which can be attributed to⁸²Br in undisturbed substitutional sites of Fe. From the center frequency of this narrow line (B _ext=0)=201.86(13) MHz we derive the magnetic hyperfine field asB _hf(BrFe)=81.38(6) T. This value is considerably larger than the result of theoretical calculations.     

Nuclear magnetic relaxation of <Superscript>3</Superscript>He in contact with an aerogel above the Fermi temperature

The spin kinetics of ³He in an aerogel has been studied above the Fermi temperature. The magnetic relaxation times T ₁ and T ₂ of adsorbed, gaseous, and liquid ³He in a 95% silica aerogel at a temperature of 1.5 K have been determined as functions of frequency by means of pulse nuclear magnetic resonance. It has been found that the time T ₁ is linear in frequency in all three cases, whereas T ₂ is independent of frequency. To explain the observed behavior of the longitudinal relaxation rate, a theoretical model of relaxation in the adsorbed layer of ³He taking into account the filamentary structure of the aerogel is proposed.     

High-resolution selective reflection spectroscopy in intermediate magnetic fields

We have measured the modifications of frequency-modulated selective reflection spectra of the CsD ₂ line recorded with circularly polarized light by a longitudinal magnetic field in the range 120–280 G. The spectra recorded with ⁺ and ^– polarizations were found to be qualitatively different, but are well described by a theoretical model based on the diagonalization of the hyperfine-Zeeman Hamiltonian. The technique presented here is a simple way for investigating fully resolved complex Zeeman spectra in moderate magnetic fields and may find applications in the investigation of anisotropies in long-range atom-surface interactions.     

Negative muon hyperfine transition rate in aluminum

The residual polarization of theF ^– hyperfine state of ^–27Al has been investigated as a function of applied transverse magnetic field strength using standard TD- ^–SR techniques. TheF ^– precession frequency is –0.2623(5) [theoretical value: –0.2622] times that of the free muon in the same field. The observed muon decay electron asymmetry in theF ^– state decreases with increasing magnetic field strength, due to initial precession in the opposite direction of theF ⁺ state, which most muon initially populate, followed by a rapid transition to theF ^– state. A fit of the data to this model indicates a transition rateR=41(9)s^–1, in good agreement with theoretical predictions. This method can be used to determineR experimentally in other cases where it is too fast to be observed directly.     

Why PeV scale left–right symmetry is a good thing

We report the results of in-situ characterization of ⁸⁷Rb atom cloud in a quadrupole Ioffe configuration (QUIC) magnetic trap after a radio-frequency (RF) evaporative cooling of the trapped atom cloud. The in-situ absorption images of the atom cloud have shown clear bimodal optical density (OD) profiles which indicate the Bose–Einstein condensation (BEC) phase transition in the trapped gas. Also, we report here, for the first time, the measured variation in the sizes of the condensate and thermal clouds with the final frequency selected in the frequency scan of the RF-field for evaporative cooling. These results on frequency-dependent sizes of the clouds are consistent with the theoretical understanding of the BEC phenomenon in the trap.     

The magnetic dipole moment of the 91 keV state of147Pm

The magnetic dipole interaction of the 91 keV state of¹⁴⁷Pm in an environment of metallic neodymium has been investigated by a time-differential perturbed angular correlation (TDPAC) experiment. The measurement was performed in an external magnetic field of 2.94 (3) T at room temperature. From the Larmor precession frequency the magnetic dipole moment of the 91 keV state is derived as =+3.22(16) _K. The enhancement of the external magnetic field by the paramagnetic 4f shell determines the ionicity of the Pm ion as Pm³⁺ in metallic and as Pm⁴⁺ in non-metallic sources.     

Searches for Lorentz violation in 3He/129Xe clock comparison experiments

We discuss the design and performance of a very sensitive low-field magnetometer based on the detection of free spin precession of gaseous, nuclear polarized ³He or ¹²⁹Xe samples with a SQUID as magnetic flux detector. Characteristic spin precession times $T_2^\ast$ of up to 115 h were measured in low magnetic fields (about 1 μT) and in the regime of motional narrowing. With the detection of the free precession of co-located ³He/¹²⁹Xe nuclear spins (clock comparison), the device can be used as ultra-sensitive probe for non-magnetic spin interactions, since the magnetic dipole interaction (Zeeman-term) drops out in the weighted frequency difference, i.e., Δω?=?ω _He ???γ _He /γ _Xe ·ω _Xe . We report on searches for Lorentz violating signatures by monitoring the Larmor frequencies of co-located ³He/¹²⁹Xe spin samples as the laboratory reference frame rotates with respect to distant stars (sidereal modulation).     

Uniqueness and global Markov property for Euclidean fields: The case of general polynomial interactions

We give a general method for proving uniqueness and global Markov property for Euclidean quantum fields. The method is based on uniform continuity of local specifications (proved by using potential theoretical tools) and exploitation of a suitable FKG-order structure. We apply this method to give a proof of uniqueness and global Markov property for the Gibbs states and to study extremality of Gibbs states also in the case of non-uniqueness. In particular we prove extremality for ₂ ⁴ (also in the case of non-uniqueness), and global Markov property for weak coupling ₂ ⁴ (which solves a long-standing problem). Uniqueness and extremality holds also at any point of differentiability of the pressure with respect to the external magnetic field.     

Progress of the nEDM experiment at the Paul Scherrer Institute

Advances in experimental searches for a neutron Electric Dipole Moment (nEDM, d _n ) are motivated by the potential discovery of a new source of CP violation beyond the Standard Model of particle physics. The nEDM experiment at the Paul Scherrer Institute (PSI), which with accumulated sensitivity of 1.09 × 10^?26 e?cm (September 2016) is currently the most sensitive nEDM experiment worldwide, uses the Ramsey technique of separated oscillatory fields applied to stored ultracold neutrons. The nEDM measurements depend upon precise information about the magnetic field, which is monitored by a ¹⁹⁹Hg co-magnetometer and an array of ¹³³Cs magnetometers. The principle of the magnetic field measurement is based on the optical detection of the Larmor precession frequency of atoms polarized by optical pumping. In this article we present the recent progress of the nEDM experiment as well as details of a magnetic field measurements with special focus on the laser-operated array of high-sensitivity ¹³³Cs magnetometers.     

Study of atomic spectral lines in a magnetic field with use of a nanocell with the thickness <Emphasis Type="Italic">L</Emphasis> = λ

We propose a technique which we call “L = λ Zeeman technique” (LZT) for investigation of the transitions between the Zeeman sublevels of the hfs structure of alkali metal atoms in external magnetic fields. The technique is based on the employment of a nanocell with the thickness of the Rb atom vapor column equal to the wavelength of the laser radiation, 780 nm, resonant with the atomic rubidium D₂ transition. At the laser intensities of about 1 mW/cm² in the transmission spectrum of the nanocell narrow (～ 30 MHz) resonant peaks of reduced absorption appear localized exactly on the atomic transitions. In magnetic fields these peaks are split and their amplitudes and frequency positions depend on the magnetic field strength. The theoretical model well describes the experimental results.     

Vertex form factors of the rho-meson nucleon interaction at low momentum transfer

We calculated the one pion loop contributions to the form factors of the rho-nucleon interaction within a field theoretical model using effective Lagrangians. The results show that the tensor interaction is likely to be described well within such an approach. We obtain a magnetic coupling in the range of 3.5–7.1 atQ ²=0, depending on the choice of pion-nucleon form factor and a dipole form for theQ ² dependence tensor form factor with a scale of roughly 900 MeV for space-like momentum transfer. The results agree with the findings of the recent analysis of thep-N interaction and support a small scale parameter (0.5 GeV) for the pion-nucleon form factor.This work is supported by BMFT (06BO7027) and COSY-KFA Jülich (41140512)     

Effect of an applied magnetic field on the performance of a sis receiver near 300 GHz

We have successfully constructed and tested a superconductor-insulator-superconductor (SIS) receiver for operation at 265–280 GHz using 1 m² area Nb–AlO _x –Nb tunnel junctions fabricated at Stony Brook. The best performance to date is a double sideband (DSB) receiver noise temperature of 129 K at 278 GHz. We find that suppression of the Josephson pair currents with a magnetic field is essential for good performance and a stable DC bias point. Fields as high as 280 gauss have been used with no degradation of mixing performance. We illustrate the improvement in the intermediate frequency (IF) output stability with progressively increasing magnetic fields.     

Structure of magnetic resonance in <Superscript>87</Superscript>Rb atoms

Magnetic resonance at the F_g = 1 \( \rightleftarrows \)F_e = 1 transition of the D₁ line in ⁸⁷Rb has been studied with pumping and detection by linearly polarized radiation and detection at the double frequency of the radiofrequency field. The intervals of allowed values of the static and alternating magnetic fields in which magnetic resonance has a single maximum have been found. The structure appearing beyond these intervals has been explained. It has been shown that the quadratic Zeeman shift is responsible for the three-peak structure of resonance; the radiofrequency shift results in the appearance of additional extrema in resonance, which can be used to determine the relaxation constant Γ₂. The possibility of application in magnetometry has been discussed.     

MHD theory of the stability of a viscous sphere

The problem of the stability of a sphere in the presence of a toroidal magnetic field is discussed with account taken of a small viscosity with respect to perturbations of the type n=m=2, which are decisive in the theory of the stability of spherical figures. Within the framework of the linear theory it has been established that a small kinematic viscosity in the presence of a toroidal magnetic field of order of smallness ^r, where r0.25, has no effect on the nature of the stability of the spherical figures under discussion but only changes the frequency of the vibrations. The vibration frequency is found as a function of the magnetic field induction and the kinematic viscosity.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 32–35, April, 1982.     

Precise measurement of the magnetic moment of doubly closed shell − 1 nucleon nucleus15O(I π1/2−,T 1/2=122 s)

The magnetic moment of¹⁵O(I=1/2^–,T _1/2=122 s) has been measured precisely by use of the -NMR detection of¹⁵O in TiO₂ as, |(¹⁵O; 1/2^–)|=0.71951 (12) µ_N. The effective nucleon mass in the nuclei around mass number 16 was discussed using the isoscalar moment deduced in connection with the magnetic moment of¹⁵N.     

Ultrahigh magnetic field diagnostic with spectral profile calculation

We report the theoretical results on use of neon as a tracer element to measure the multi-megagauss magnetic field, which is induced in the ultrahigh intense laser-matter interactions. The shape of Zeeman splitting of spectral line for transition of He-like neon are calculated for high-intensity laser produced quasi one-components plasma with the consideration of the electron collision broadening, electron collision shift and magnetic field splitting. The results show that all of the Zeeman splitting spectrum can be identified under Rayleigh criterion for the plasma with the electron temperature from 10 to , the magnetic field from 10⁶ to and the electron density . With both the electron temperature and magnetic field increasing, the requirement for the resolution power of the spectrometer decreases. If a spectrometer with the resolution power of 1/1000 is used, the measurement of the quasistatic magnetic field by Zeeman splitting of spectral lines is applicable when quasistatic magnetic field is larger than some tens of megaGauss.