Alien converts between the rpm, deb and Slackware tgz file formats. If you want to use a package from another distribution than the one you have installed on your system, you can use alien to convert it to your preferred package format and install it.
apt-get install alien
Use the following to install your rpm file :
alien -i rpm_file_to_install.rpm
Converting rpm file to deb:
alien -k rpm_file_to_convert.rpm
Then you will need to use the following command to install the deb file resulted :
dpkg -i name_of_created_deb_file.deb