[1] Harvard University,Department of Physics and Harvard School of Engineering and Applied Sciences
[2] Cambridge,Department of Chemistry
[3] Massachusetts 02138,Department of Physics
[4] USA,undefined
[5] Columbia University,undefined
[6] New York,undefined
[7] New York 10027,undefined
[8] USA,undefined
[9] University of North Texas,undefined
[10] Denton,undefined
[11] Texas 76203,undefined
[12] USA,undefined
[13] Present addresses: Department of Applied Physics,undefined
[14] Chalmers University of Technology,undefined
[15] SE-412 96 Göteborg,undefined
[16] Sweden (J.M.); TU Eindhoven,undefined
[17] Institute for Complex Molecular Systems and Department of Mechanical Engineering,undefined
[18] PO Box 513,undefined
[19] 5600 MB Eindhoven,undefined
[20] The Netherlands (H.M.W.); School of Physics,undefined
[21] Georgia Institute of Technology,undefined
[22] Atlanta,undefined
[23] Georgia 30332,undefined
[24] USA (A.F.-N.); Institute of Physics,undefined
[25] University of Tsukuba,undefined
[26] Tsukuba 305-8571,undefined
[27] Japan (K.M.).,undefined