Time locked subsampling (TLSS) in electron paramagnetic resonance (EPR) involves the steps of (i) translation of the signal from a microwave carrier to an intermediate frequency (IF) carrier where the (IF) offset between the signal oscillator and local oscillator frequencies is synthesized, (ii) sampling the IF carrier four times in an odd number of cycles, say 4 in 3, where the analog-to-digital (A/D) converter is driven by a frequency synthesizer that has the same clock input as the IF synthesizer, (iii) signal averaging as required for adequate signal to noise, (iv) separating the even and odd digitized words into two separate signal channels, which correspond to signals in phase and in quadrature with respect to the IF carrier, i.e., I and Q, and (v) detecting the envelope of I and also of Q by changing the signs of alternate words in each of the two channels. TLSS detection has been demonstrated in three forms of pulse EPR spectroscopy at X band: saturation recovery, pulse electron–electron double resonance, and free induction decay. The IF was 187.5 MHz, the A/D converter frequency was 250 MHz, the overall bandwidth was 125 MHz, and the bandwidths for the separate I and Q channels were each 62.5 MHz. Experiments were conducted on nitroxide radical spin labels. The work was directed towards development of methodology to monitor bimolecular collisions of oxygen with spin labels in a context of site-directed spin labeling.

1.
J. S.
Hyde
,
H. S.
Mchaourab
,
T.
Camenisch
,
J. J.
Ratke
,
R. W.
Cox
, and
W.
Froncisz
,
Biophys. J.
71
,
2622
(
1998
).
2.
J. A.
Giordmaine
,
L. E.
Alsop
,
F. R.
Nash
, and
C. H.
Townes
,
Phys. Rev.
109
,
302
(
1958
).
3.
C. F.
Davis
, Jr.
,
M. W. P.
Strandberg
, and
R. L.
Kyhl
,
Phys. Rev.
11
,
1268
(
1958
).
4.
M.
Huisjen
and
J. S.
Hyde
,
Rev. Sci. Instrum.
45
,
669
(
1974
).
5.
P. W.
Percival
and
J. S.
Hyde
,
Rev. Sci. Instrum.
46
,
1522
(
1975
).
6.
J. S. Hyde, in Time Domain Electron Spin Resonance, edited by L. Kevan and R. N. Schwartz (Wiley, New York, 1979), pp. 1–30.
7.
J. S. Hyde, in Foundations of Modern EPR, edited by S. S. Eaton, G. R. Eaton, and K. M. Salikhov (World Scientific, Singapore, 1998), pp. 607–618.
8.
W. L.
Hubbell
,
H. S.
Mchaourab
,
C.
Altenbach
, and
M. A.
Lietzow
,
Structure
4
,
779
(
1996
).
9.
M.
Nechtschein
and
J. S.
Hyde
,
Phys. Rev. Lett.
24
,
672
(
1970
).
10.
J. S.
Hyde
,
W.
Froncisz
, and
C.
Mottley
,
Chem. Phys. Lett.
110
,
621
(
1984
).
11.
R. A.
Strangeway
,
H. S.
Mchaourab
,
J. R.
Luglio
,
W.
Froncisz
, and
J. S.
Hyde
,
Rev. Sci. Instrum.
66
,
4516
(
1995
).
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