DRAMIŃSKI - Nir spectroscopy

[1] M.Weitz, A.Huber, F.Schmidt-Kaler, D.Leibfried, and T.W.Hänsch, Phys. Rev. Lett. 72, 328 (1994).
[2] M.Weitz, A.Huber, F.Schmidt-Kaler, D.Leibfried, W.Vassen, C.Zimmermann, K.Pachucki, T.W.Hänsch, L.Julien, and F.Biraben, Phys. Rev. A 52, 2664 (1995).
[3] S.Bourzeix, B.de Beauvoir, F.Nez, M.D.Plimmer, F.de Tomasi, L.Julien, and F.Biraben, Phys. Rev. Lett. 76, 384 (1996).
[4] Th.Udem, A.Huber, B.Gross, J.Reichert, M.Prevedelli, M.Weitz, and T.W.Hänsch, Phys. Rev. Lett. 79, 2646 (1997).
[5] B.de Beauvoir, F.Nez, L.Julien, B.Cagnac, F.Biraben, D.Touahri, L.Hilico, O.Acef, A.Clairon, and J.J.Zondy, Phys. Rev. Lett. 78, 440 (1997).
[6] A.Huber, Th.Udem, B.Gross, J.Reichert, M.Kourogi, K.Pachucki, M.Weitz, and T.W.Hänsch, Phys. Rev. Lett. 80, 468 (1998).
[7] K.Pachucki, D.Leibfried, M.Weitz, A.Huber, W.König, and T.W.Hänsch, J. Phys. B 29, 177 (1996).
[8] S.Lundeen and F.Pipkin, Phys. Rev. Lett. 46, 232 (1981).
[9] C.Zimmermann, R.Kallenbach, and T.W.Hänsch, Phys. Rev. Lett. 65, 571 (1990).
[10] F.Schmidt-Kaler, D.Leibfried, S.Seel, C.Zimmermann, W.König, M.Weitz, and T.W.Hänsch, Phys. Rev. A 51, 2789 (1995).
[11] A.Huber, B.Gross, M.Weitz, and T.W.Hänsch, Phys. Rev. A 58, R2631 (1998).
[12] B.Gross, A.Huber, M.Niering, M.Weitz, and T.W.Hänsch, Europhys. Lett., 44(2), 186 (1998).
[13] A.Huber, B.Gross, M.Weitz, and T.W.Hänsch, Phys. Rev. A 59, 1844 (1999).
[14] J.Reichert, M.Niering, R.Holzwarth, M.Weitz, Th.Udem and T.W.Hänsch, Phys. Rev. Lett. 84, 3232 (2000).
[15] M.Niering, R.Holzwarth, J.Reichert, P.Pokasov, Th.Udem, M.Weitz, T.W.Hänsch, P.Lemonde, G.Santarelli, M.Abgrall, P.Laurent, C.Salomon and A.Clairon, Phys. Rev. Lett. 84, 5496 (2000).
[16] B.deBeauvoir, C.Schwob, O.Acef, L.Jozefowski, L.Hilico, F.Nez, L Julien, A.Clairon, and F.Biraben, Eur. Phys. J. D 12, 61{93 (2000).
[17] Th.Udem, R.Holzwarth, and T.W.Hänsch, Nature 416, 233 (2002).
[18] M.Fischer, N.Kolachevsky, M.Zimmermann, R.Holzwarth, Th.Udem, and T.W. Hänsch, M. Abgrall, J.Grünert, I Maksimovic, S.Bize, H.Marion, F.Pereira Dos Santos, P Lemonde, G.Santarelli, P.Laurent, A.Clairon, M.Haas, U.D.Jentschura, and C.H.Keitel, Phys. Rev. Lett. 92, 230802 (2004).
[19] S.Bize, S.A.Diddams, U.Tanaka, C.E.Tanner, W.H.Oskay, R.E.Drullinger, T.E.Parker, T.P.Heavner, S.R.Jefferts, L.Hollberg, W.M.Itano, and J.C.Bergquist, Phys. Rev. Lett. 90, 150802 (2003)
[20] E.Peik, B.Lipphardt, H.Schnatz, T.Schneider, and Chr.Tamm, S.G.Karshenboim, Phys. Rev. Lett. 93, 170801 (2004).

By comparing data taken in 2003 [18] with earlier measurements in 1999 [15] we can set an upper limit on the variation of the 1S-2S transition frequency of (-29 ± 57) Hz within 44 months. To derive limits on the drift rates of fundamental constant such as the fine structure constant, we combine these measurements with other optical frequency measurements in Hg+ and in Yb+ performed at NIST, Boulder/USA [19] and at PTB, Braunschweig/Germany [20] respectively. This combined method gives precise and separate restrictions for the fractional time variation of the fine structure constant and the Cs nuclear magnetic moment measured in Bohr magnetons. The latter is a measure of the drift rate of the strong interaction.

According to the Schrödinger theory 2 times the 2S-4S transition frequency should be half of the 1S-2S transition frequency. By longitudinal Doppler-free two-photon excitation of a cold hydrogen beam we have observed the beat frequency between the frequency doubled IR radiation, used to drive the 2S-4S transition, and the blue light used to drive the 1S-2S transition after being frequency doubled. If the well-known fine and hyperfine structure and the first order correction of the Dirac energies due to the finite nuclear mass is subtracted, this beat contains a combination of Lamb shifts of the involved levels. On the other hand, if one believes in QED, a more accurate value of the proton charge radius can be extracted from those frequencies.

The 486 nm radiation of the dye laser is transfered through an optical fiber to the frequency comb [17] to compare it phase-coherently with a Cs atomic clock. In this way the absolute frequency of the hydrogen 1S-2S transition is determined with one of the most precise measurement tools. Subtracting the Lamb shift from the measured frequency a value for Rydberg may be derived from the remainder. On the other hand if one uses a value for the for Rydberg constant determined in a different experiment and a measured for the 2S Lamb shift [8] a value of the 1S Lamb shift may be derived. This is an important result since the Lamb shift of the 1S level is the largest of all hydrogen energy levels and it is not accessible to radio frequency methods. The most general way to determine the constants given above is to use not only the 1S-2S transition frequency but all available hydrogen data [16].

In the 1S-2S experiment hydrogen atoms are excited by longitudinal Doppler-free two photon excitation at 243 nm. This radiation is generated by a frequency doubled ultrastable dye laser at 486 nm. The UV radiation is then resonantly enhanced in a linear cavity inside a vacuum chamber . Atomic hydrogen from a gas discharge is directed through a nozzle cooled with liquid helium. The cold atomic beam is oriented along the axis of the enhancement resonator. After the atoms have passed a distance L, usually around 10 cm, a small electric field that mixes the metastable 2S state (lifetime 1/7 sec) with the fast decaying 2P state is applied. To reduce the residual second order Doppler-effect we use a delayed detection scheme where the fluorescence at 121 nm is detected only after the exciting light has been switched off for a period T, typically between 0.5 and 1.8 ms. In this way we set an upper limit on the second order Doppler-shift below 1 kHz.

For many years high resolution spectroscopy on atomic hydrogen has been essential for the development and testing of fundamental theories. Today the precise determination of transition frequencies and relations among them provides one of the most rigorous verification of QED [1,2,3]. The most precise values of the Rydberg constant to date are derived from optical frequency measurements in atomic hydrogen [4,5]. From the comparison of the transition frequencies in hydrogen and deuterium the deuteron structure radius can be extracted. Since the deuteron is the simplest nucleus (besides the proton) knowledge about its structure is essential to test nuclear models [6]. A survey of recent developments in high resolution hydrogen spectroscopy and its theoretical treatment is presented in [7].

f(1S-2S) = 2 466 061 102 474 851(34) Hz

R = 10 973 731.568 525(84) m-1

L1S = 8 172.840(22) MHz