We determine the frequency of the Yb I 1 S0 − 1 P1 transition at 399 nm using an optical frequency comb. Although this transition was measured previously using an optical transfer cavity [D. Das et al., Phys. Rev. A 72, 032506 (2005)], recent work has uncovered significant errors in that method. We compare our result of 751 526 533.49 ± 0.33 MHz for the Yb-174 isotope with those from the literature and discuss observed differences. We verify the correctness of our method by measuring the frequencies of well-known transitions in Rb and Cs, and by demonstrating proper control of systematic errors in both laser metrology and atomic spectroscopy. We also demonstrate the effect of quantum interference due to hyperfine structure in a divalent atomic system and present isotope shift measurements for all stable isotopes.

We observed up to 15 paramagnetic resonance Raman lines due to collective multiple spin Aips within the Zeeman split Mn + ground state S5/2 in a quantum well structure with semimagnetic Cd() 9gMnpp2Te wells and nonmagnetic Cdp76Mnp24Te barriers with external magnetic fields B", 7.5T. This effect appears near resonance with the heavy-hole transitions of narrow quantum wells in the Voigt backscattering geometry and can be explained by a precession of the total spin of all Mn2+ ions in the suni of external and exchange field (8,", iB,", h), the latter produced by the heavy hole. PACS numbers: 73.40.Lq, 76.30.Fc, 78.30.Fs In dilute magnetic II-VI semiconductors (DMS), e.g. , in Cd~, Mn Te (x~0.2), the large exchange interaction between the extended charge carriers and the localized electrons [3d5(6Ssi2) in Mn~+] manifests itself in the giant Zeeman splitting of the s-p hybridized valence and conduction band-edge states with a g factor near 100 and in the formation of magnetic polarons (MP) [1]. The MP consists of a fluctuating magnetization cloud of the Mn + spins associated with a localized charge carrier.A ferromagnetic spin correlation within the orbit of the carrier is produced [2]. The MP is usually studied at low or zero external field. In the following we present experimental insight into the formation process of a similar phenomenon, a magnonlike collective precession motion of the Mn2+ spins in an effective magnetic field which is a superposition of the external field B, , along the quantum well interfaces (~~x) and the exchange field B,", h oriented normal (~~z) to the interfaces.We observe in the Raman spectrum a large number (n ) 5) of simultaneous spin flips Am = 1 of Mn~+ ions.Because of the Zeeman ground-state sextet of a single Mn + ion, this clearly has to be a simultaneous transition of many ions. We interpret these findings in short as follows: In the homogeneous external magnetic field in the Voigt geometry (B,", x) the Mn + moments are oriented along B,", . After a localized exciton has been created; i.e. , B", h~~z; has been switched on, the effective field B,ff = B"t + B, ,h has changed its direction and the I component of the total angular momentum I of the Mn + ions in the interaction volume is no longer conserved. The quantum energy of the light emitted in the recombination process of the exciton is reduced with respect to the incoming laser energy by the amount spent to reorient the ensemble of Mn + ions, which is an integer number n of energy steps of a single spin fIip. ' In the case of bulk Cd~, Mn, Te or MBE (molecular beam epitaxy) grown epilayers of Cd& Mn, Te with low x, where effects of large Mn clusters are negligible, magnetic excitations have been observed previously by means of Raman spectroscopy, which are caused by spin flips of electrons in the conduction band [3] and by spin fIips Amq = 1 and Amq = 2 of a single Mn + within the Zeeman levels of the S ground state. These are the paramagnetic resonance (PR) signals, which linearly shift with B, gL»d; = 2. The limitation Amq = ...

GaAs is usually contaminated by carbon and & IC due to its growth conditions. Acting shallon mepto-these substitutional impurities substantially determine the electrical and optical behaviour of this materid. We measured the far infrared absorption spectra due to optical transitions of holes bound to these acceptors in LEC grow GaAs at T E 1.2 K, B 6 7 T and magnetic field directions Bll(lOO), ( 110) and ( 111). We present theg-values of the 1S&a gmundstate and, for the first time, the 2P3/2rs and the 2P5/Js excited states. We use a graphical melhod to analyse the splitting of the levels mentimed earlier using only symmetry considerations.

No abstract

No abstract