  We have analyzed HST/NICMOS2 F110W, F160W, F165M, and F207M band images
covering the central 1'x1' of the cluster associated with Mon R2 in order to
constrain the Initial Mass Function (IMF) down to 20 Mjup. The flux ratio
between the F165M and F160W bands was used to measure the strength of the water
band absorption feature and select a sample of 12 out of the total sample of
181 objects that have effective temperatures between 2700 K and 3300 K. These
objects are placed in the HR diagram together with sources observed by
Carpenter et al. (1997) to estimate an age of ~1 Myr for the low mass cluster
population. By constructing extinction limited samples, we are able to
constrain the IMF and the fraction of stars with a circumstellar disk in a
sample that is 90% complete for both high and low mass objects. For stars with
estimated masses between 0.1 Msun and 1.0 Msun for a 1 Myr population with Av <
19 mag, we find that 27+-9% have a near-infrared excess indicative of a
circumstellar disk. The derived fraction is similar to, or slightly lower than,
the fraction found in other star forming regions of comparable age. We
constrain the number of stars in the mass interval 0.08-1.0Msun to the number
of objects in the mass interval 0.02-0.08 Msun by forming the ratio,
R**=N(0.08-1Msun)/N(0.02-0.08Msun) for objects in an extinction limited sample
complete for Av < 7 mag. The ratio is found to be R^**=2.2+-1.3 assuming an age
of 1 Myr, consistent with the similar ratio predicted by the system IMF
proposed by Chabrier (2003). The ratio is similar to the ratios observed
towards the Orion Nebula Cluster and IC 348 as well as the ratio derived in the
28 square degree survey of Taurus by Guieu et al. (2006).
