EPR Spectrometers at Frequencies Below X-band
5. SPECTROMETER DESIGN
5.5 Other Spectrometer Types
An induction EPR spectrometer, operating at 900 MHz, described by Duncan (1967), had a single-tum coil in a coaxial cavity. The coil was positioned such that no (-80 dB) microwave flux cuts the coil, except at EPR resonance.
An electrically-detected magnetic resonance spectrometer, detecting EPR at 900 MHz (Sato et al., 2000), was designed to study semiconductors. Up to 50 W could be incident on the sample in a 4.4 em diameter, 1 em long, bridged LGR whoseQwas 510.
Frequency modulation has been used only rarely in EPR because of the high Q of the EPR resonator. Hirata et al. (2002) combined frequency modulation with an electronically tunable 1.1 GHz surface-coil resonator and an automatic tuning control (ATC) system. Approximately the same signal-to-noise ratio was obtained with frequency modulation of 28 kHz and magnetic field modulation of 90 kHz.
Ultra-low-field (earth's magnetic field) EPR spectrometers have been developed by Moussavi and coworkers (Duretetal., 1991, 1992; Kemevez et al., 1992) and by Gebhardt and Dormann (1989) for use as magnetometers.
References to these and other overall spectrometer designs are summarized in Table 1.
2. EPRSPECTROMETERS AT FREQUENCIES BELOW X-BAND 73 Table I. Spectrometer Systems
Frequency, Comment
Spectrometertype variable
0-285 Gauss 1.845 MHz 1-300 MHz 1.2-15 MHz 4.4,9, and 27.4 MHz 5 to 450 MHz
10-70 MHz ultrasonic 10-120 MHz 19.3 MHz 20 MHz
30-100 MHz
30MHz
30, 65, 320 MHz, 9 GHz 40, 80, 210 MHz 56 MHz 57 MHz
60 MHz
77 MHz 80 MHz 80 MHz
for measuring weak magnetic fields in the 0.4-21 Oersted range
').J4coaxial line oscillator-detector circuit
earth 's magnetic field magnetometer
used 3 g sample ofDPPH FlO detection with NMR spectrometer, Gaussmeter applications
hybrid junction, DBM, saturation recovery, no details given
for sound absorption in paramagnetic substances magicT, DBM, lock-in amplifier
no details given
Clapp-oscillator, tankcircuit in Dewar, Helmholtz coils, 50 Hz magnetic field modulation similar to Decorps and Fric (1972) spectrometer, samplecan beat 77 K
dispersion spectrometer; no details given
Alpha Scientific Labs spectrometers
circulator at 210 MHz; hybrid junction at 40 and 80 MHz magnetometer
Broadline NMR spectrometer, observed half-field transition for DPPH
Helmholtz magnet, Colpitts oscillator, 30 Hz magnetic field modulation and phase-sensitive detection
acoustic paramagnetic resonance marginal oscillator, 0.5mL samples
no details given
Reference Chirikov, 1959
Matheson and Smaller, 1955 Duretet al., 1991
Gebhardt and Dormann, 1989 Garstenset al.,1954 Dormannet al., 1983
Kume and Mizoguchi, 1985;
Mizoguchi and Kume, 1985 Golenishchev-Kutuzov and Kharakhash 'yan, 1965 Hatch and Kreilick, 1972 Misraetal.,1973 Bruin and Bruin, 1956 Fric and Mignot, 1975
Grobetet al., 1971 Singer, 1962
Decorps and Fric, 1972 Duretetal.,1992 Verdelinetal.,1974
Lloyd and Pake, 1954
Antokol'skiietal.,1977 Kent and Mallard , 1965 Barbarin and Germain , 1975
Frequency, Comment Reference Spectrometertype
100 MHz crystal-controlled oscillator Hutchinson and Mallard , feeds the Helmholtz coil 1971
resonator through a 10 dB directional coupler
100-450 MHz metals in glasses N. S. Garifyanov, doctoral dissertation, Kazan University, 1965, cited by Abdrachmanov and Ivanova, 1973
100-1000 MHz crossed coil resonator, Borel and Manus, 1957 Helmholtz coil magnet
135 MHz sample coil and transmission Benedek and Kushida, 1960 line make up part of the
oscillator
193.3 MHz 1 or 4 KHz modulation, sample Matsuiet al., 1993; Terakado cooled in N2gas et al., 1998
ca. 200 MHz reflection resonator, magic T, Bolaset al., 1996 quadrature detection, imaging
system
220 MHz pulsed samples up to 50 mL Alecciet al., 1998a,b 237 MHz combined PEDRI and CW EPR, McCallumet al., 1996b
hybrid coupler, DBM, LGR
240-360 MHz homodyne RF circuit, LGR, 400 McCallumet al., 1996a mLsamples
250 MHz imaging system Halpernet al., 1989
250 MHz sized for human whole-body Symons, 1995 imaging
250 MHz Pulsed imaging Quineet al., 2002; Rinard et
al.,2002a,b c 280 MHz AFC via movable diaphragm Hill and Wyard, 1967
that changes the length of the cavity; superheterodyne detection
280 MHz imaging system Alecciet al., 1992b
280 MHz quartz oscillator feeds a Dijretet al., 1994 Helmholtz excitation coil
orthogonal to a solenoidal detection coil
280 MHz pulsed DNP, LGR Alecci and Lurie, 1999
300 MHz EPR of metals at 4 K Feher and Kip. 1955
300 MHz push-pull oscillator induction- EI'sting,1960 coupled to sample coil;
electromagnet modulated at 6 KHz
300 MHz transmission mode Cook and Stoodley, 1963
2. EPRSPECTROMETERS AT FREQUENCIES BELOWX-BAND 75 Frequency,
Spectrometer type 300, 700, 900 MHz 300 MHz pulsed
300MHzCW 300,600 MHz 302 MHz 310,930 MHz 315 MHz
680 MHz EPR, 27.7 MHzNMR 700 MHz 750 MHz 900 MHz 900 MHz
I GHz I GHz I GHz 1-2 GHz 1-1.8 GHz L-band L-band
1-2 GHz
1.3GHz 1.8 GHz pulsed
2GHz
Comment LODESR
50-70 ns pulses, 350-400 ns recovery time, FID detection, imaging system
imaging system
similar to spectrometer of Feher and Kip, 1955
operation down to 0.3 K coaxial hybrid ring, superheterodyne detection DPPH sample in oscillator-detector assembly
combined CW EPR and CW NMR spectrometer rapid scan imaging imaging system induction spectrometer electrically detected magnetic resonance, BLGR
designed for aqueous samples circulator, surface coil Pulsed, forin vivo imaging solid state source, circulator, reflection resonator tunable, homodyne circulator, stub tuner, BLGR added to commercial EPR used iron-core electromagnet and console ofa Varian E112
imaging system
3D gradients
pulsed microwaves and rapid field scan for fast-passage recovery measurement of relaxation times
circulator, helix, 360 Hz field modulation; PIN modulator
Reference
Yokoyamaet al., 1997a, 1997b
Bourget al., 1993;
Murugesanet al., 1997, 1998;
Afeworkiet al., 2000;
Subramanianetal., 2002 Brivatiet al., 1991; Stevens and Brivati, 1994
Algeret al., 1959 Medvedevet al., 1976 Duncan and Schneider, 1965 Marcley,1961
Satoet al ., 1997
Oikawaet al., 1995; Ogata, 1995
Heet al., 1999 Duncan, 1967 Satoet al., 2000 Brown, 1974 Nilgeset al., 1989 Giuseppeet al., 2001 Giordanoet al., 1976 Dahlberg and Dodds, 1981 Onoet al ., 1986
Nishikawaet al., 1985; Fujii and Berliner, 1985; Berliner and Fujii, 1985; Berliner and Koscielniak, 1991
Zweier and Kuppusamy, 1988, 1994; Kuppusamyet al., 1994; Kuppusamy et al., 2001
Colacicchiet al., 1988;
Alecciet al., 1992b
Rannestad and Wagner, 1963
Adkins and Nolle, 1966
Frequency, Comment Reference Spectrometer type
permitted saturation recovery measurements
S-band pulsed circulator, LGR, 1 KW TWT, Clarksonet 01., 1989, 1992 DBM detector
S-band for process control Hyde and Froncisz, 1981
S-band, pulsed ESE, circulator, LGR, 1 KW Hankiewiczet 01., 1993;
TWT,4.2K Romanelliet 01., 1994
3GHz for determination of the sign of Charru, 1956 the Lande g-factor
10 cm wavelength (3 hybrid ring in place of the magic Strandberget 01., 1956
GHz) T that was used at 3 ern
wavelength ; AFC
3.8-4.4 GHz klystron and pulsed TWT, Bowers and Mims, 1959 rectangular TEoI Icavity, for
saturation recovery
1001 MHz, zero-field for study of organic triplet states Schmidt, 1972 at 1.2 K with I W microwave
pulses, circulator, DBM
PEDRI, Overhauser 69,74,197, 198,208 MHz Grucker and Chambron,
effect 1989; Grucker, 1990;
Grucker and Chambron, 1993; Guiberteau and Grucker, 1997 PEDRI, Overhauser field cycling Lurieet 01., 1988, 1998 effect
EPRbyDNP EPR at 62, 66, 69, 72, 74, 198 Guiberteau and Grucker,
MHz 1996; Gruckeret 01., 1996
LODESR 300 MHz Nicholsonet 01., 1994b, 1996
EPR and DNP; CW 9.5 mT, 267 MHz for EPR, 404 Ardenkjaer-Larsenet 01.,
EPR, pulsed NMR KHzforNMR 1998