摘要:

A fluorescence microscope for the detection of spatially resolved single molecules at low temperature has been developed. The main part consists of a microscope objective which is inserted in superfluid helium. Two versions of the optical system are described. Both setups have a high numerical aperture and thus high collection efficiency. A video camera with an image intensifier is used to detect the fluorescence images. Detection of single molecule fluorescence has been achieved. It was even possible to visualize individual fluorescing molecules on a video monitor in real time. Spectroscopic applications of this parallel detection scheme are discussed. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146868

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We demonstrate simultaneous trapping and spatial separation of the two stable rubidium isotopes in a magneto‐optical trap. To realize this novel type of isotope separation, we have built a compact diode laser which is frequency‐stabilized by optical feedback from a diffraction grating, and frequency‐modulated by a direct microwave modulation of the bias current from a yittrium iron garnet tuned oscillator. Use of the single diode laser with microwave sidebands provides much ease and flexibility in the applications of a magneto‐optical trap. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146869

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A novel fiber optic velocity interferometer for velocity measurements of moving surfaces has been developed and tested. The interferometer is based on optical fibers or fiber coupled components only and therefore is compact, portable, easy to align, and enables measurements in hard to reach locations. It also does not require a source of long coherence length (only a few wavelengths, regardless of the optical path difference or the surface displacement). This interferometer removes the directional ambiguity of the acceleration using a [3×3] optical coupler. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146895

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

An apparatus is described for the measurement of second‐order nonlinear optical properties via hyper‐Rayleigh scattering with 1 cm−1spectral resolution of the scattered light. The setup allows a complete investigation of the polarization dependence of the second‐harmonic scattered light. The combination of good spectral resolution, polarization analysis, and high sensitivity allows the determination of accurate polarization ratios of the scattered light. Consequently, information on the relative magnitude of hyperpolarizability components may be inferred from the measurements. Liquid phase measurements of a number of pure organic solvents including substituted benzene compounds are reported with approximately 5% uncertainty in the relative scattered intensities. Vapor phase measurements are also possible using the same apparatus, allowing a separation of the intrinsic molecular nonlinearities from contributions to hyper‐Rayleigh scattering due to intermolecular interactions. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146870

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The origin of spurious and irreproducible signals in the measurement of the hyper‐Rayleigh scattering (HRS) of solutions is investigated. A new cell design, coupled with continuous solution filtration through a 20 nm filter, is shown to improve the reproducibility of the measurement to ±5%. A transverse cell dimension of ∼2 mm reduces absorption of the second harmonic. A simple monochromaticity test is used to identify luminescence, and we recommend that it is made routinely. Scattering from the [Ru(bipy)3]2+cation, attributed to HRS by Zyssetal. [Chem. Phys. Lett.206, 409 (1993)], appears to be largely due to two‐photon excited luminescence. The reliability of calibration procedures is examined, and some revised hyperpolarizabilities are reported. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146871

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A process has been developed to hand grind and polish infrared KBr lenses with a wide choice of focal lengths. These lenses are designed for coupling the infrared (IR) beam from a Fourier transform infrared spectrometer into a hot filament chemical vapor deposition reactor. These IR lenses are ground using a glass lens as a mold; the mold lens is a commercial glass lens used for spectacles and is available in a wide range of focal lengths. Rough grinding begins with ♯100 sandpaper and followed by a sequence of fine grinding steps under ethanol: ♯400 SiC powder, ♯600 SiC powder, and emery powder. Polishing is done with a CeO slurry in water followed by a chamois cloth moistened with ethanol. As an indication of the surface finish of the lenses, a flat KBr window that is hand ground and polished in the above manner has a transmission of ≳89% at 8000 cm−1and ≳91% at 500 cm−1; the commercially polished KBr window has a transmittance of 92% throughout this spectral range. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146872

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The beam‐rocking method in the scanning electron microscope can show either the inner surface of a deep hole or the outer surface of a parallel‐sided pillar in ways that are not possible when scanning in the usual way. This has been demonstrated using test samples of both kinds. It is believed that this method can be successfully applied to examine deep holes and narrow pillars of micrometer dimensions by applying computer control and data analysis techniques of the kind that are used in automated semiconductor fabrication and/or metrology systems. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146873

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A vacuum compatible Kelvin probe force microscopy (KPFM) is presented. Difficulties in operating KPFM in a vacuum were overcome by utilizing the direct cantilever resonance frequency detection in the tip height control whereas the indirect resonance frequency detection scheme was used in primordial KPFM. The potential measurement sensitivity was improved by 14 dB compared to that in air. It is due to the increased cantileverQvalue and the reduction in the interference from the tip height detection signal because potential measurement is conducted using the cantilever’s second resonance while tip height control was conducted using the first resonance. A silicon wafer whose surface is partially doped with arsenic by ion implantation was observed, and surface potential difference at the junctions were clearly imaged. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146874

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We describe a non‐contact, non‐optical distance feedback control system for scanning probe microscopes that detects the surface damping of a vibrating probe. The feedback signal is derived from an electrical impedance change in a dithering piezoelectric element with attached scanning tip. The system incorporates an arbitrary‐impedance bridge that maximizes detection sensitivity of the surface damping‐induced impedance change as the tip approaches and interacts with the sample. In addition, an auxiliary circuit greatly improves reliability by making the feedback signal insensitive to the phase of the impedance change. The complete detection network can sense changes of −80 to −100 dB down to the level of 1 &mgr;V in a bandwidth of ≳1 kHz. The feedback system has demonstrated topographic height sensitivity of ∼0.5 A˚ and dynamic range of ≳60 dB. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146875

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We present a three‐dimensional micropositioner using the inertial slider principle which is used to position an optical fiber in an atomic force microscope. It uses only two moving parts as the sideways and vertical motions are realized by either moving a cylinder along its axis or rotating it around its axis and translating the rotation into an approximately vertical motion. The device operates reliably in a baked ultrahigh vacuum system, allows positioning with sub‐&mgr;m accuracy, and has a forward range of 11.3 mm, a sideways range of 5 mm, and a vertical range of approximately 5 mm. The measured speeds without extra load fall in the range between 1.6 and 3.3 mm/min, in good agreement with the amplitude and curve shape of the applied drive signal. The minimal step size allowing consistent motion is below 25 nm. ©1996 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1146876

出版商:AIP    

年代:1996

数据来源: AIP