Identification of Rydberg States inNa2by Two-Step Polarization Labeling

Abstract

Ten new excited *A g states and five new excited *ng states of Na 2 have been identified with the use of the two-step polarization labeling technique. The electronic energies of these states form a molecular Rydberg series. By extrapolating the dissociation energies, vibrational constants, and rotational constants of these Rydberg states it is possible to obtain good estimates of the same quantities for the -^22g ground state of Na 2 + .PACS 35.20.Gs, 35.20.Pa In recent years, the Rydberg states of the atoms have been the subject of many experiments. However, over the last fifty years the Rydberg states of only a few diatomic molecules have been studied. 1 The vibrational-rotational structure of molecules complicates the electronic absorption spectra considerably. However, the absorption spectrum of a molecule can be greatly simplified by use of polarization labeling because transitions from only one selected vibrationalrotational level are observed.The technique of two-step polarization labeling 2 has been demonstrated to be an extremely effective tool for the study of excited states in diatomic molecules. As in polarization spectroscopy, 3 a resonant polarized pulsed pump laser induces an optical anisotropy in the levels of a single vibrational-rotational transition. A broadband linearly polarized pulsed probe laser will experience a change in polarization for frequencies resonant with transitions which have a common level with the pump-laser transition. If the probe is passed through a crossed polarizer, only those frequencies which interacted with a level of the pumped transition will be transmitted. A spectrograph can then be used to record the probe spectrum photographically. The absorption spectrum is greatly simplified because probe signals can only occur from the two levels of the pump transition. Therefore, P-, (?-, and R-branch transitions can be readily identified.Probe signals corresponding to transitions from the upper level of the pump transition to higher excited states can be distinguished from absorption of oriented ground-state molecules by the absence of two-step signals on a delayed probe spectrum. 2 Alternatively, dipole selection rules for the oriented molecules, and the different vibrational-rotational constants, provide ways to recognize new states. 4 The use of a broadband probe makes it possible to cover large regions of the optical part of the spectrum on a single photographic plate. This is very useful when searching for new excited states, since several different vibrational bands of an excited state will appear on a single plate. Such vibrational sequences yield immediate information about the vibrational-rotational structure of the excited state.In this experiment, single vibrational-rotational transitions in the X-B band of Nag (Ref. 5) were labeled by the pulsed pump laser. A series of broadband probes which covered the region from 7000 to 5500 A were used to probe transitions to higher excited states. In Fig. 1, a typical probe spectrum is shown. The long bright lines FIG. 1...

Theoretical study of low‐lying electronic states of the LiRb+ molecular ion: Structure, spectroscopy and transition dipole moments

“…They have used in their study the same formalism used in our work. As it seems in Table 5, there is a good agreement between the available theoretical works39–43 and our ab‐initio study. In addition, our ground state equilibrium distance ( R e ) presents a satisfying agreement as well as the well depth ( D e ) with the work of Azizi et al42, 43 We find for R e and D e , respectively, 7.70 a. u. and 3912 cm −1 and they found 7.54 a. u. and 4193 cm −1 .…”

“…For the ground‐ and low‐lying electronic states, we have extracted the spectroscopic constants ( R e , D e , T e , ω e , ω e χ e , and B e ) from their numerical potential energy curves. These spectroscopic constants are presented in Table 5 and compared with the other theoretical works 39–43. For our best knowledge, the only theoretical works performed for LiRb + molecular ion are those of Patil et al41 and Azizi et al42, 43 and no experimental spectroscopic informations have been found on such system.…”

“…To our best knowledge, there are no experimental studies and only few theoretical studies have been performed on the LiRb + molecular ion. The first theoretical works of the LiRb + molecular ion have been realized by Bellomonte et al39 and Carlson et al40 Patil and Tang41 have made a model potential calculation for the LiRb + molecular ion, where they have determined the equilibrium distance ( R e ) and the well depth ( D e ) of the ground state. More recently, Azizi et al42, 43 have performed an ab‐initio calculation for the LiRb + molecular ion.…”

Data readout from compact disks by a laser pickup with diffraction optics

“…x 'E,.. where n as high as 12 has been observed (Carlson et al 1980(Carlson et al , 1981. Furthermore, only singlet states have been identified to be involved in the observed two-photon transitions of Na,.…”

“…This result shows significant deviation from the expected ideal cubic laser power dependence, see equation (3). This, however, is not a surprise because real molecular states, i.e., A 'E: and the two-photon excited gerade states , Carlson et al 1980, King et a1 1981, Vasudev et al 1981, Morgan et a1 1982, Woerdman 1978, Muller and Hertel 1981, have been involved in the multiphoton ionisation process. When the laser power exceeds the level of saturation of the first transition, which is akin to a constant population of Na2(A 'E:), the number of ions produced will obviously not be proportional to the laser power density raised to the third power.…”