Other

Rutgers, The State University of New Jersey

Mks Instruments, Inc.

Brooks Automation Gmbh

Barbara Jane Hinch

Alexei Ermakov

Alexei Victorovich Ermakov

Gerardo A Brucker

Michael N Schott

Scott C Heinbuch

Kenneth D Van Antwerp, Jr

G Jeffery Rathbone

Alexei V Ermakov

Methods of operation of electrostatic ion trap mass spectrometers in which ions are autoresonantly driven at selected higher integer (&#x3e;2) multiples of ion oscillation frequencies are provided. Excitation at multiples higher than the fundamental or double the fundamental ion oscillation frequency significantly improves both signal intensity and mass resolution. Each method allows excitation exclusively at one selected frequency that is an integer multiple of an ion's natural oscillation frequency, and thereby virtually eliminates ion excitation at unwanted harmonic frequencies. The resultant mass spectra are therefore clean, and do not display spectral features associated with rf excitation at unintended multiple harmonic frequencies. This has been demonstrated explicitly for 4&#xd7; and 6&#xd7; modes, and it is fully implementable at any odd or even multiples of ion oscillation frequencies. With implementation of a new method, mass spectrometers can be operated at faster mass scan rates, giving faster response times, without degradation of signal to noise or resolution over the existing technology instruments. Equivalently, with implementation of a new method, mass spectrometers can be operated with superior signal to noise ratios without degradation of response times or resolution.

Electrostatic ion trap mass spectrometer utilizing autoresonant ion excitation and methods of using the same

An electrostatic ion trap confines ions of different mass to charge ratios and kinetic energies within an anharmonic potential well. The ion trap is also provided with a small amplitude AC drive that excites confined ions. The mass dependent amplitudes of oscillation of the confined ions are increased as their energies increase, due to an autoresonance between the AC drive frequency and the natural oscillation frequencies of the ions, until the oscillation amplitudes of the ions exceed the physical dimensions of the trap, or the ions fragment or undergo any other physical or chemical transformation.

Electrostatic ion trap

An ion trap includes an electrode structure, including a first and a second opposed mirror electrodes and a central lens therebetween, that produces an electrostatic potential in which ions are confined to trajectories at natural oscillation frequencies, the confining potential being anharmonic. The ion trap also includes an AC excitation source having an excitation frequency f that excites confined ions at a frequency of about twice the natural oscillation frequency of the ions, the AC excitation frequency source preferably being connected to the central lens. In one embodiment, the ion trap includes a scan control that mass selectively reduces a frequency difference between the AC excitation frequency and about twice the natural oscillation frequency of the ions.

The inventive apparatus measures workfunction values using deflection of an electron beam without direct contact of the electron beam with the sample surface. The apparatus, mounted within a vacuum chamber, includes an electron gun, a position sensitive electron detector, and a sample. The sample is located such that an electron beam emanating from the gun can approach the surface and then be deflected into the position sensitive electron detector. Workfunction values are then derived from a measured deflected-electron position distribution.

Electron beam apparatus for work function measurements

The inventive apparatus is capable of accurate contactless sample conductance measurements. In accordance with the invention, a three coil apparatus for inductive conductance measurements comprises at least three coils, (or inductive devices,) a radio frequency (RF) generating device in conjunction with electronic circuitry for radio frequency amplitude measurement and comparison of radio frequency amplitude signals. The attainable accuracy is improved over that achieved using other conventional non-contact means by processing the differences of RF amplitude signals observed across pairs of sensing coils. Also, this invention does not require more complex RF signal processing, such as analysis of in-phase and quadrature voltage data. In a preferred embodiment, the natural resonance frequencies of the two sensing coils are tuned slightly off the RF driving frequency such that a monotonic response across a wide range of the sample's conductivity is achieved. The sensitivity of the apparatus to low sample conductances is thereby further enhanced.

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Edison, NJ, United States of America

Barbara Jane Hinch