Optical Hole Burning Research Articles

Hole burning and optically detected fluorine NMR inPr3+: CaF2

The interactions between ${\mathrm{Pr}}^{3+}$ ions in a tetragonal site of 0.01-at.% ${\mathrm{Pr}}^{3+}$:Ca${\mathrm{F}}_{2}$ and the surrounding nuclei are investigated, primarily by means of optically detected NMR (ODNMR). This technique is based on the fact that hole burning in the 5941-\AA{} $^{3}H_{4}\ensuremath{\leftrightarrow}^{1}D_{2}$ transition takes place due to coupling between the rare-earth ion and neighboring $^{19}\mathrm{F}$ nuclear spins. ODNMR lines are identified which are due to nearest-neighbor (NN), next-nearest-neighbor (NNN), and interstitial ($i$) fluorines. The distorted positions of the NNN fluorines are determined from the ODNMR data, but this is impossible for the other near neighbors due to strong covalent-bonding effects. Physical models for the hole-burning and refilling processes are proposed which agree qualitatively with the hole shapes and ODNMR line intensities, and with the observation of rf-assisted optical hole burning when a strong magnetic field ${H}_{0}$ is applied parallel to ${C}_{4}$.

Site-selection and Zeeman spectroscopy of theS1↔S0transition of magnesiumporphin inN-octane at 4·2 K

Site selection spectroscopy combined with a study of the Zeeman effect of the MgP · ethanol complex (MgP = magnesiumporphin) in a n-octane single crystal is reported. The splitting of the 1 Eu state is identified with the 0-0 y transition 195 cm-1 above the 0-0 x transition. The value of the electronic orbital angular momentum Λ = 4·4 and the Jahn-Teller interaction is very weak. Laser excitation into the 0-0 x transition leads to reversible photochemistry. In this process the interaction of ethanol with the porphin nucleus is attenuated and the crystal field splitting reduced to 22 cm-1. The photochemistry enables optical hole burning from which the homogeneous widths of the 0-0 transitions are determined. SCF-PPP calculations are performed to mimick the MgP · ethanol complex. The calculations satisfactorily explain the differences between the ethanol complex and its photoproduct.

Optical hole burning by superhyperfine interactions in CaF_2:Pr^3+

Optical hole burning has been observed in the 5941-A transition of Pr(3+) in a charge-compensated tetragonal site of CaF(2) . The Pr(3+) ground state is doubly degenerate and shows a large first-order hyperfine splitting, which is clearly resolved because of the very narrow inhomogeneous linewidth of 650 MHz. The hole burning involves a new mechanism, in which optically induced spin flips of neighboring nuclei (here (19)F) shift the optical transition frequency outside its homogeneous linewidth. This mechanism was confirmed by optical rf double resonance.

Measurement of the Anomalous Nuclear Magnetic Moment of Trivalent Europium

An order-of-magnitude reduction of the nuclear magnetic moment of trivalent europium due to hyperfine-induced magnetic shielding was predicted by Elliott in 1957. With use of optical hole burning and optically detected nuclear quadrupole resonance in YAl${\mathrm{O}}_{3}$: ${\mathrm{Eu}}^{3+}$, this shielding has been measured for the first time. We find that the ground-state moment is reduced to 21% of its intrinsic value, while the moment in the excited $^{5}D_{0}$ state is unaffected.

Optical hole burning and matrix effects in a phthalocyanine complex of ruthenium(II)

A doubling of the origin is observed in the low-temperature electronic absorption spectrum of the complex carbonyl(pyridine)-phthalocyaninatoruthenium(II) in glassy matrices. The effect is studied by optical hole burning and results suggest a non-degenerate singlet ground state of near C 2v symmetry to be invoked.

Optical measurement of spin-lattice relaxation of dilute nuclei: LaF3:Pr3+

We describe a method of measuring spin-lattice relaxation rates of dilute nuclei using optical hole burning. This was applied to $^{141}\mathrm{Pr}$ nuclei doped into La${\mathrm{F}}_{3}$ at low concentrations (0.01 to 2.0 at.%). The observed relaxation rates varied by about two orders of magnitude between 2 and 4.5 K. At the lowest concentrations the data are interpreted in terms of two mechanisms: resonant two-phonon (Orbach) relaxation with a ${57\ensuremath{-}\mathrm{c}\mathrm{m}}^{\ensuremath{-}1}$ activation, and praseodymiumlanthanum cross relaxation. At higher concentrations an additional hole-filling process was observed and attributed to homonuclear Pr-Pr dipolar coupling. Theoretical estimates of the phonon-induced relaxation rates are given and agree approximately with experimental values.

Optical hole burning in ruby

We report experimental and theoretical studies of optical hole burning in the inhomogeneous ${R}_{1}$ line of ruby at low temperatures. Both Stark-shifting and pump-probe techniques using narrow-band single-frequency lasers were employed. In addition to the observation of narrow holes, we have found that a large (up to 70%) decrease in absorption occurs outside the hole and that the relative size of this decrease is constant over the entire inhomogeneous line. This effect is ascribed to fast resonant cross-spin relaxation in the ground-state levels which drives all spins within the optically pumped volume to a common spin temperature. A theoretical model is formulated which describes the power-broadened hole shapes as well as the off-resonance decrease in the absorption coefficient. Fair agreement with experiment is obtained for the case of a magnetic field applied along the $c$ axis; however, sizable deviations from the theory are seen for zero field. We conclude that further studies are needed to elucidate the nature of the Al superhyperfine-broadening mechanism. An upper limit of 1200 nm is deduced for the size of macroscopically broadened regions in ruby.

Modulation of optical FID and structure of absorption line due to superhyperfine interaction in ruby

Modulation of optical free induction decay (FID) and structure of R 1 absorption line due to superhyperfine interaction in ruby have been observed by using Stark-switching and Stark-sweeping techniques, respectively. The inhomogeneous broadening is effectively eliminated by a narrow optical hole burning. Frequency and phase characteristics of the FID signal have also been examined. The agreement between experimental results and theoretical calculations is quite satisfactory.

Population hole-burning using a triplet reservoir: S 1 ← S 0 transition of zinc porphin in n-octane

Optical hole-burning has been observed in the S 1 ← S 0 absorption of zinc porphin in n-octane by selective depletion of the ground state population and storage in the mestastable triplet state. In this way the homogeneous linewidths of S 1 ← S 0 for molecules in A and B sites of n-octane were measured between 1.6 and 4.5 K. Thermally induced dephasing was observed for B-site molecules with an activation energy of 14 cm −, equal to the separation between the two electronic components of S 1.

Coherent transients observed by Stark switching in ruby having narrow optical hole burning

By using the Stark switching technique we observed new coherent transient signals in ruby at low laser intensities, which are unique in solids where T 1 ⪢ T 2. It was confirmed that the existence of narrow optical hole burning before the switching plays an essential role in giving rise to the signals. The effects of the multiple optical hole burning were also observed in the time domain. Assuming the existence of the holes, the signals can well be interpreted by linear system analysis.

Optical hole-burning in the ultraviolet spectrum of 3,4,9,10-dibenzpyrene at room temperature

Ultraviolet fluorescence spectra are presented for 3,4-benzpyrene, 1,12-benzeperylene and 3,4,9,10-dibenzpyrene, which were obtained by single-laser, consecutive two-proton excitation. Experiments using two-laser excitation have permitted the study of fluorescence line-narrowing in the spectrum of dibenzpyrene at 300 K in hexane solution. These unique observations are interpreted in terms of optical site-selection.

Observation of multiple optical hole burning in ruby

Direct observation of optical hole burning in ruby is made by using a Stark-field sweeping technique. In addition to the main hole at the laser frequency, new side holes at the shifted frequencies are observed. The origin of the side holes is considered to be due to the population redistribution of resonant ions in the ground state 4A 2 by spin-spin cross relaxation and that in the excited state Ē( 2E) by spin-lattice relaxation. Differences from the observation by Szabo and the applicability to high resolution spectroscopy are discussed.

Observation of hole burning and cross relaxation effects in ruby

In this paper we report, for the first time, the observation of optical hole burning in a solid, ruby. In addition, we describe experimental results which show that optical saturation of the inhomogeneously broadened ${R}_{1}$ line in ruby at 4.2\ifmmode^\circ\else\textdegree\fi{}K occurs not only for ions in resonance with the saturating radiation but also for ions at frequencies up to about 50 MHz away from the radiation frequency. This result and others are consistent with a model in which cross relaxation occurs in the ground-state levels between ions in resonance with the laser beam and nonresonant ions.

Sideband detection of optical hole burning in ruby

Sideband detection of optical hole burning in ruby