Electron spin resonance spectrometer and method for using same

• US 9,507,004 B2
• Filed: 04/03/2014
• Issued: 11/29/2016
• Est. Priority Date: 07/31/2013
• Status: Active Grant

• Current Assignee: National Institute of Standards and Technology (Government of the United States of America), Penn State Research Foundation
• Original Assignee: Penn State Research Foundation, THE GOVERNMENT OF THE UNITED STATES OF AMERICA, AS REPRESENTED BY THE SECRETARY OF COMMERCE
• Inventors: Campbell, Jason P., Cheung, Kin P., Ryan, Jason T, Lenahan, Patrick M.
• Primary Examiner(s): FULLER, RODNEY EVAN
• Application Number:
  US14/244,494
• Publication Number:
  US 20140210473A1
• Time in Patent Office: 971 Days
• Field of Search: 324/316
• US Class Current: 1/1
• CPC Class Codes: G01N 24/10 by using electron paramagnetic resonance G01N24/12 takes precedence
• CPC Class Codes: G01R 33/60 using electron paramagnetic resonance G01R33/24, G01R33/62 take precedence

Abstract

An electron spin resonance spectrometer includes a bridge to transmit an excitation frequency and to receive a signal frequency; a probe electrically connected to the bridge and comprising: a first conductor in electrical communication with the bridge to transmit the signal frequency to the bridge; a shorting member electrically connected to the first conductor to transmit the excitation frequency to a sample, to produce the signal frequency, and to transmit the signal frequency to the first conductor; and a second conductor electrically connected to the shorting member; and a magnet disposed proximate to the probe.

Claims

1. An electron spin resonance spectrometer comprising:

a bridge to transmit an excitation frequency and to receive a signal frequency;

a probe electrically connected to the bridge and comprising;

a first conductor in electrical communication with the bridge to transmit the signal frequency to the bridge;

a shorting member electrically connected to the first conductor to transmit the excitation frequency to a sample, to produce the signal frequency, and to transmit the signal frequency to the first conductor; and

a second conductor electrically connected to the shorting member; and

a magnet disposed proximate to the probe.

2. The electron spin resonance spectrometer of claim 1, further comprising a modulation coil disposed on a surface of the magnet such that the modulation coil is interposed between the magnet and the sample,

wherein the modulation coil is configured to receive a bias voltage, a reference frequency, or a combination comprising at least one of foregoing.

3. The electron spin resonance spectrometer of claim 2, further comprising a detector connected to the bridge to detect a detection frequency.

4. The electron spin resonance spectrometer of claim 3, wherein the bridge comprises:

a reference arm to transmit the excitation frequency to a combiner;

a sample arm comprising a circulator and configured to transmit the signal frequency and the excitation frequency reflected by the shorting member to the combiner; and

the combiner to balance the bridge and to transmit a combined frequency toward the detector,

wherein the bridge is configured to be balanced in the absence of the signal frequency at the combiner, and the bridge is configured to be unbalanced in the presence of the signal frequency at the combiner.

5. The electron spin resonance spectrometer of claim 4, wherein the bridge further comprises a local oscillator arm comprising a mixer, the bridge being configured to produce the detection frequency and to transmit the detection frequency to the detector.

6. The electron spin resonance spectrometer of claim 3, wherein the detector is a phase sensitive detector.

7. The electron spin resonance spectrometer of claim 6, further comprising a reference oscillator configured to transmit the reference frequency to the modulation coil and to the detector.

8. The electron spin resonance spectrometer of claim 1, further comprising an excitation source to produce the excitation frequency and to transmit the excitation frequency to the bridge.

9. The electron spin resonance spectrometer of claim 1, wherein the electron spin resonance spectrometer is configured to acquire an electron spin resonance spectrum in response to varying the excitation frequency present at the shorting member, a magnetic field strength applied to the sample from the magnet, or a combination comprising at least one of the foregoing.

10. The electron spin resonance spectrometer of claim 1, wherein the shorting member is a lumped circuit comprising:

a first conductor extension electrically connected to the first conductor;

a second conductor extension electrically connected to the second conductor; and

a probe tip electrically shorting the first conductor to the second conductor, the probe tip configured to transmit the excitation frequency to the sample.

11. The electron spin resonance spectrometer of claim 10, wherein the shorting member further comprises a basal member such that the first conductor extension and the second conductor extension are disposed on the basal member, and

the probe tip extends from the first conductor extension and the second conductor extension such that a portion of the probe tip is not disposed on the basal member.

12. The electron spin resonance spectrometer of claim 10, wherein a length of the probe tip that is configured to transmit the excitation frequency to the sample has a length from 500 nm to 500 μ

m.

13. The electron spin resonance spectrometer of claim 1, wherein the magnet is surroundingly disposed around the probe.

14. The electron spin resonance spectrometer of claim 13, wherein the electron spin resonance spectrometer is configured to acquire an electron spin resonance spectrum with the excitation frequency from 1 MHz to 100 GHz, inclusive of each excitation frequency.

15. The electron spin resonance spectrometer of claim 1, wherein the electron spin resonance spectrometer has an excitation volume of less than 100 μ

m³.

16. The electron spin resonance spectrometer of claim 1, wherein the electron spin resonance spectrometer is configured to receive the sample being disposed proximate to the shorting member and external to the magnet.

17. The electron spin resonance spectrometer of claim 1, wherein the electron spin resonance spectrometer is configured to acquire an electron spin resonance spectrum in the absence of a cavity.

18. The electron spin resonance spectrometer of claim 1, wherein the probe is a surface scanning probe.

19. The electron spin resonance spectrometer of claim 1, wherein the probe is a non-resonant, near-field probe.

20. A method for acquiring an electron spin resonance spectrum, the method comprising:

disposing a sample in an electron spin resonance spectrometer comprising;

a bridge comprising a sample arm and a reference arm;

a probe electrically connected to the bridge and comprising;

a first conductor electrically connected to the bridge;

a shorting member electrically connected to the first conductor; and

a second conductor electrically connected to the shorting member;

a detector electrically connected to the bridge;

a magnet disposed proximate to the probe and the sample; and

a modulation coil interposed between the magnet and the sample;

transmitting an excitation frequency from an excitation source to the sample through the sample arm and the shorting member;

modulating a magnetic field present at the sample from the magnet at a reference frequency applied to the modulation coil;

absorbing, by the sample, the excitation frequency;

producing a signal frequency at the shorting member;

transmitting the signal frequency from the shorting member toward the detector;

combining the signal frequency from the sample arm and the excitation frequency from the reference arm to produce a detection frequency; and

detecting, by the detector, the detection frequency as a function of changing the excitation frequency or a magnetic field strength present at the sample to acquire the electron spin resonance spectrum,

wherein the sample is disposed external to the probe, the magnet, and the modulation coil.