Prof. Dr. Wolfgang Hüttner

N25/426

22831

wolfgang.huettner@physik.uni-ulm.de

Our fields of interest belong to atomic and molecular Physics, and can briefly be characterized as follows:

  • Electric and magnetic properties of atoms and molecules in excited electronic states

  • Singlet-triplet interactions

  • Localization of rovibrational levels of (dark) triplet states

 

We use mainly high resolution laser spectroscopy, especially

  • saturation (Lamb-dip) techniques

  • Doppler-free two-photon absorption

  • Microwave-Optical Double Resonance (MODR)

  • Zeeman and Stark effects

 

Results

  • Recently we have determined the atomic magnetizabilities (magnetic susceptibilities) in several quantum states of Li, Na, K, Rb, Cs, and have obtained preliminary results for a few singlet and triplet levels of the two-electron systems Ca, Sr, and Ba. Fields up to 4.5 Tesla have been employed for detecting the second- order Zeeman effects. Methods for the suppression of the electronic orbital and spin first-order Zeeman effects had to be developed.

P. Otto, Dissertation Ulm (1999)

P. Otto, M. Gamperling, M. Hofacker, T. Meyer, V. Pagliari, A. Stifter, M. Krauss, W. Hüttner, Chem.Phys. 2002, in press

W. Hüttner, P. Otto, M. Gamperling, Phys. Rev. A 54(1996)1318

  • We have previously shown for H2C=S that Zeeman tuned perturbations of known singlet levels (avoided crossings with M components of near-by triplet levels) can be used to localize the zero-field energies of rovibronic triplet states. Efforts of understanding the nature of the underlying singlet-triplet interaction have recently been successful: it could be shown that a vibronic coupling mechanism is responsible. 

W.Ulrich, Dissertation Ulm (1999) 

W. Ulrich, W. Hüttner, J. Molec. Spectrosc. 200(2000)182 

  • In an attempt to determine the complete set of rotational g-factors and magnetizabilities of the S1 excited electronic state of the thioformaldehyde molecule, H2C=S, we have extended the range of our MODR spectrometer from 2.5 to about 75 GHz. Some zero-field rotational transition frequencies measured in the S1(41Ã1A2) electronic state were found as listed in the following Table 1. 

Table 1

   

  

nexp / MHz

ncalc / MHzc)

D / MHz

1 1 0  ¬  1 1 1

      813.2 a)

       827.621

       -14.42

2 1 1  ¬  2 1 2 

  2502.86(10) b) 

  2482.770

         20.09 

3 1 2  ¬  3 1 3

  4926.60(10) b)

  4965.251

       -38.65

1 0 1  ¬  0 0 0

31419.16(10) b)

31416.981

           2.18

2 0 2  ¬  1 0 1

62836.25(10) b)

62831.365

           4.89

2 1 2  ¬  1 1 1

61754.12(10) b)

62003.253

     -249.13

2 1 1  ¬  1 1 0

63443.52(10) b)

63658.401

     -214.88

8 1 7  ¬  8 1 8

29667.84(12) b)

29773.040

     -105.2

            a) J.C. Petersen, D.A. Ramsay, T. Amano, Chem.Phys.Lett. 103(1984)266.

            b) M. Wagner, Dissertation Ulm (2002). 

            c) Calculated with the deperturbed constants from Clouthier et al., J. Chem. Phys. 101 (1994) 7300.

Many of the Zeeman spectra obtained for these transitions appeared highly perturbed. We found local (narrow) and global (broad banded) avoided crossings with M components of triplet states. In measuring the Doppler-free LIF Zeeman splittings of the S1(41111) ¬ S0(00) transition (at a frequency of 
(16775.31308 ± 0.00003) cm-1),we were able to accurately determine the Zeeman level field functions of the S1(41111) rovibrational state, and in turn from the Zeeman splittings of the transition 212 ¬ 111 in Table 1 also those of the level S1(41212). The three MN = -1, 0, 1 magnetic sublevels show a strong global crossing near 3.4 Tesla (which we cannot explain yet), while the -2, -1, 0 components show local crossings near 0.15, 0.26, and 0.61 Tesla, respectively (which are probably caused by the F1 321 triplet of the 4262ã3A2 vibronic state). Work is in progress which aims at the assignment of the perturbers, and a quantitative analysis of the perturbation mechanisms.

When we combine the zero-field S1(41111) ¬ S0(00) frequency from above with the MODR zero-field frequencies in Table 1 we arrive at the following level energies E(NKaKc) of the  41Ã1A2 vibronic state of H2C=S, in the following 
Table 2.

                          Table 2

NKaKc

E(NKaKc)/cm-1

111

16775.31308(3)

110

      75.34021(3)

212

      77.37298(3)

211

      77.45646(3)

                          M.Wagner, Dissertation Ulm (2002).

International agreement on the signs of g-factors
16 authors from eight countries, most of them well-known workers in molecular spectroscopy, have suggested to generally accept the principle that parallel vectors of angular momentum and magnetic moment require a positive, antiparallel ones a negative sign of the associated g-factor. This implies that the orbital and spin electron g-factors are negative. For details see

J.M. Brown, R.J. Buenker, A. Carrington, C. Di Lauro, R.N. Dixon, R.W. Field, J.T. Hougen, 
W. Hüttner, K.Kuchitsu, M. Mehring, A.J. Merer, T.A. Miller, M. Quack, D.A.Ramsay, L. Veseth, and R.N. Zare, 
Mol.Phys. 98 (2000) 1597

 

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