State-specific Lifetime Determination of the a3Pi
State in CO
Two different techniques have been applied to measure the lifetime of the
lowest rotational levels in the metastable a3Pi(v=0,omega=1) state of CO.
First, measurement of the absolute absorption cross-section for several
absorption lines of the a(v=0)<--X(v=0) transition yields an Einstein
coefficient of A_{0,0}=97±3 s^{-1}. In combination with the experimentally
determined branching ratios for the a<--X transition, the lifetime of
each component of the a3Pi(v=0, omega=1, J=1) Lambda-doublet is determined
to be 3.67±0.20 ms. Secondly, detection of the spin-forbidden fluorescence
at two positions in the molecular beam downstream from the excitation region
as a function of velocity of the molecules directly probes the exponential
decay. With this technique the lifetime of the lower component of the same
a3Pi(v=0, omega=1, J=1) Lambda-doublet is determined to be 3.4±0.4
ms, while for the upper component a value of 3.8±0.5 ms is found.
R.T. Jongma, G. Berden, and G. Meijer.
State-specific lifetime determination of the a3Pi state
in CO, J. Chem. Phys. 107 (1997) 7034-7040.
Stark shift measurements of a3Pi CO
A scheme is presented for confinement of neutral molecules in stable orbits
on the basis of the linear Stark effect in a properly designed electrostatic
trap. Based on Stark shift measurements in electric fields up to 140 kV/cm,
an electrode configuration that is, under realistic experimental conditions,
capable of confining metastable CO(a3Pi) molecules with velocities up to
22 m/s is described. Metastable CO molecules can be laser-prepared inside
the trap and their trajectories can be directly visualized via spatially
resolved detection of their fluorescence.
R.T. Jongma, G. von Helden, G. Berden, and G. Meijer.
Confining CO molecules in stable orbits.
Chem. Phys. Lett. 270 (1997) 304-308.
A reanalysis of the k3Pi state of CO
The k3Pi state of the CO molecule is investigated in the region between
91000 and 97000 cm-1 via 1+1 Resonance Enhanced Multiphoton Ionization
spectroscopy on CO molecules prepared in a single quantum level of the
aPi (v=1) state. A new vibronic band is found which is at lower energy
than the vibrational ground state reported in the literature, leading to
a reassignment of the vibrational numbering of the k3Pi state. The rotationally
resolved spectra of the k3Pi (v=0-6) <-- aPi (v=1, J=1, Omega=1) of
12CO and 13CO have been observed and analyzed, confirming the new vibrational
labeling and providing a full set of molecular constants of the k3Pi valence
state.
G. Berden, R.T. Jongma, D. van der Zande, and G. Meijer.
A reanalysis of the k3Pi state of CO,
J. Chem. Phys. 107 (1997) 8303-8310.