Spectroscopic prescription for optimal stimulated Raman transfer of ultracold heteronuclear molecules to the lowest rovibronic level

Abstract

We show that the multiplicative product of a molecular-beam excitation spectrum and an ultracold-molecule excitation spectrum, with a frequency offset appropriate to the initial ultracold-molecule level, provides the relative rate of stimulated Raman transfer (SRT) from a given high rovibrational level to the lowest rovibronic level, i.e., the v = 0,J = 0 level of the ground electronic state for photoassociated (and magnetoassociated) ultracold molecules. This product spectrum clearly indicates the optimal pathways for SRT, even when the two component spectra are completely unassigned. We illustrate this specifically for the case of KRb.

Spectroscopy of the double minimum 3 3ΠΩ electronic state of 39K85Rb

“…Hence, we have performed high resolution spectroscopy of various electronic states (both excited and ground) of KRb over the years. 2,[8][9][10][11][12][13][14][15][16] In this paper, we rea) Electronic mail: jbanerjee@phys.uconn.edu b) Present address: Wyatt Technology Corporation, Santa Barbara, California 93117-3253, USA. c) Also at The Kavli Institute for Theoretical Physics, University of California at Santa Barbara, Santa Barbara, California 91036-4030, USA.…”

Direct photoassociative formation of ultracold KRb molecules in the lowest vibrational levels of the electronic ground state

“…However, as is evident in Figure 6, the 2 3 Σ + ←X 1 Σ + transitions are actually nearly as strong as the singlet-singlet REMPI transitions. Similarly efficient transitions between these two states are also reported in [23][24][25]. This occurs because there are five excited electronic states in this energy region, 2 1 Σ + , 1 1 Π, 2 3 Σ + , 1 3 Π and 3 1 Σ + , which undergo mutual perturbations at various internuclear distances.…”

“…As is evident from the figure, there are still some unassigned lines in this region. These are likely to be transitions to vibrational levels of the same intermediate states beyond the range reported in [23][24][25].…”

“…This gives rise to very complicated coupling and hence the participating states are often not of pure singlet or triplet character. This is probably facilitating not only the detection of the lowest vibrational levels of X 1 Σ + via the 2 3 Σ + state in KRb with very good efficiency [23,24], but also the formation of these low-lying vibrational states by resonant coupling. At small internuclear distances the 2(1) state correlates to the 2 3 Σ + state and the 4(1) state correlates to 1 1 Π.…”

“…Thus the vibrational energies of the ground state and intermediate states used to assign the REMPI spectra are all well known from experiments and hence there is very little uncertainty in the assignments of our spectra. Also, we have only assigned the lines in the REMPI spectrum which can be detected via the vibrational levels of the intermediate states already observed in [23][24][25]. As a result, there are a few lines that are still unassigned.…”