Nhng tin b trong Quang hc, Quang ph vÃ ng dng VI ISSN 1859 - 4271

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Advances in Optics, Photonics, Spectroscopy & Applications VI ISSN 1859 - 4271between two energy surfaces without the fluorescence. The relaxation from S 1 is similar to thecase of S 2 . A minority of the population of S 1 is involved in the fluorescence by the transition S 1 -S 0 . The majority leave S 1 to S X by a twist of <strong>ph</strong>enyl groups. Here, we assume that the transitionsof S 2 -S 1 and S 1 -S X are made by two different modes of torsion and the S X is in the sameelectronic level with S 1 because there is a signature of spectral shift in the fluorescence of S1.The transition S X - S 0 * is a transition between two electronic states with a movement of the<strong>ph</strong>enyl groups. Finally, the transition S 0 * -S 0 , though the hot ground state and the meta-stablestate, completely fills the relaxation and allows the molecules to find the initial configurations.VI. CONCLUSIONWe have given new contributions to the understanding of <strong>ph</strong>oto-<strong>ph</strong>ysics of MG by a study ofspectroscopy time-resolved broadband. In this work, we retain the important points: observationof the transition S 2 -S n , determining the lifetimes of the absorption signal induced in the near UVspectral region, demonstration the existence of two populations "hot" and meta-stable in theground state.In the interest of the study in the ultrafast <strong>ph</strong>oto-<strong>ph</strong>ysics of other molecular systems, webelieve that our analytical model of the MG will be a reference model interes<s<strong>trong</strong>>tin</s<strong>trong</strong>>g. It can apply toall compounds of the tri<strong>ph</strong>enylmethane or the similar systems.REFERENCES[1] A. H. Gomes de Mesquita, C. H. MacGillavry, K. Eriks. Acta Crystallogr. 18, 437, 1965.[2] H. P. J. M. Dekkers, E. C. M. Kielman-Van Luyt. Mol. Phys. 31, 1001, 1976.[3] L. Angeloni, G. Smulevich, M. P. Marzocchi, J. Raman Spectroscopy, 8: 305, 1979.[4] C. W. Looney, W.T. Simpson. J. Am. Chem. Soc. 76: 6293, 1954.[5] J. Korppi-Tommola, R. W. Yip, J. Chem. 59: 191, 1981.[6] D. F. Duxbury, Chem. Rev., 93: 381-433, 1993.[7] D. Ben-Amotz, C. B. Harris, J. Chem. Phys, 86: 4856-4870, 1987.[8] M. M. Mar<s<strong>trong</strong>>tin</s<strong>trong</strong>>, P. Plaza, Y. H. Meyer, J. Phys. Chem, 95: 9310-9314, 1991.[9] M. Vogel, W. Ber. Bunsen-Ges. Rettig. Phys. Chem, 89: 962, 1985.[10] T. Förster, G. Z. Hoffmann, J. Phys. Chem., 75, 63, 1971.[11] Y. Nagasawa, Y. Ando, T. Okada, Chemical Physics Letters, 312: 161-168,1999.[12] M. Yoshizawa, K. Suzuki, A. Kubo, S. Saikan, Chem. Phys. Lett., 290: 43-48, 1998.[13] E.P. Ippen, C.V. Shank, A. Bergman, Chem. Phys. Lett. 38: 611, 1976.[14] M. Ishikawa, Y. Maruyama, Chem. Phys. Lett., 219: 416-420, 1994.[15] Ground-and Excited-State Isomerization of Tri<strong>ph</strong>enylmethane Dyes in the Femtoseconde Regime. J.Phys. Chem. A, 103: 5629-5635, 1999.[16] A. Mokhtari, L.Fini, J. Chesny, J. Chem. Phys. 7: 1551-1557, 1987.[17] A.C. Bhasikuttan, A.V. Sapre, T. Okada , J. Phys. Chem. A, 107: 3030-3035, 2003.[18] T. Robl, A. Sellmeier, Chem. Phys. Let., 147: 544-550, 1988.96
Những tiến bộ <strong>trong</strong> <strong>Quang</strong> học, <strong>Quang</strong> <strong>ph</strong>ổ và Ứng dụng VI ISSN 1859 - 4271PROSPECTS OF FLUORIDE CRYSTALS AS VACUUM ULTRAVIOLETLASER MATERIALS VIA UP-CONVERSION LUMINESCENCEMinh Pham 1 , Marilou Cadatal-Raduban 1 , Toshihiko Shimizu 1 , Masahiro Kouno 1 , KoheiYamanoi 1 , Mizuki Tsuboi 1 , Yusuke Furukawa 2 , Elmer Estacio 1 , Tomoharu Nakazato 1 ,Nobuhiko Sarukura 1 , Toshihisa Suyama 3 , Kentaro Fukuda 3,4 ,Akira Yoshikawa 4 , and Fumio Saito 41 Institute of Laser Engineering Osaka University 2-6 Yamadaoka, Suita, Osaka 565-0871 Japan2 Midorikawa Laser Technology Laboratory,The Institute of Physical and Chemical Research, 2-1Hirosawa, Wako, Saitama, 351-0198, Japan3 Tokuyama Corporation Shibuya 3-chome, Shibuya-ku, Tokyo 150-8383 Japan4 Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira,Aokuba, Sendai 980-8577, Japan.E-mail: <strong>ph</strong>minh@ile.osaka-u.ac.jpAbstract. We report the vacuum ultraviolet luminescence from up-conversion of ultravioletfemtosecond pulses in Nd 3+ :LaF 3 and Nd 3+ :LuLiF 4 , with spectral and temporal characteristics similarto 157 nm excitation. The results suggest the possibility of an all-solid-state vacuum ultraviolet lasermaterials.Keywords: Laser materials, Vacuum ultraviolet, Fluoride.I. INTRODUCTIONResearch and development of vacuum ultraviolet (VUV) laser media are con<s<strong>trong</strong>>tin</s<strong>trong</strong>>uouslyconducted for applications, such as <strong>ph</strong>otolithogra<strong>ph</strong>y [1] and spectroscopy [2]. ConventionalVUV laser sources such as excimer lasers based on rare gas dimers like Kr 2 and Xe 2 [3,4] andfrequency up-conversion in nonlinear crystals [5] are available. However, these schemes haveeither limited tunability or low conversion efficiency. Rare-earth (RE) activated ions in wideband gap dielectric crystal hosts are considered to be the most suitable laser sources to satisfy therequirements of VUV laser media due to their ease of use, reliability, and efficiency. Thesecrystals will make it possible to obtain good quality laser beam, control the spectral width, andconduct multi-wavelength operation with only one laser oscillator [6]. Trivalent Ce and Nd, areamong the RE ions that have been studied. Ce 3+ -doped crystals are shown to be excellent lasermaterials in the UV region [7]. However, its emission wavelength cannot reach VUV region [8].On the other hand, Nd 3+ is expected to be the more appropriate activator ion due to transitionsfrom the 4f25d to 4f3 that enable emission in the VUV region. For example, 172-nm laseremission was reported from Bridgman-Stockbarger method-grown Nd 3+ :LaF 3 (Nd:LaF) [9].Recently, 172-nm fluorescence from a micro-pulling down method-grown Nd:LaF has beenreported as a VUV scintillator and a prospective material for the realization of the shortestwavelength light-emit<s<strong>trong</strong>>tin</s<strong>trong</strong>>g device [10, 11]. In both reports, the 157-nm emission of an F2 laserwas used as excitation. An all-solid state laser opera<s<strong>trong</strong>>tin</s<strong>trong</strong>>g in the VUV region would be moreeconomical, more convenient, and safer to use compared to these F2 laser-pumped systems. Toachieve all-solid-state operation, the pump source must be replaced. Due to the absence of an all-97
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